I started playing Skyrim and was enjoying it but I wasn't doing any professions like Blacksmithing, because I don't find grinding in a single player game to be fun. Then I saw all of the people doing it and it turned out you needed it to have the best weapons and continue with the game.

I really just want to be a vampire/thief derping around but I still want to have houses ect but I realized as things got harder I would just be getting killed everywhere. If I didn't do things I didn't enjoy like profession grinding.

Now I come back, thinking I really haven't played this game at all and there are a ton of mods I know nothing about and I still don't know anything about these silly professions.
So my questions are:

Do I actually need to grind out these profession (like leatherworking/blacksmithing)?

Can I just be a vampire/thief and still be powerful, have access to the entire game, like the various houses?

What are the best mods to download?

You don't need to use any professions because they only make the gear better than they normally are but you can still find everything from chests and vampire/thief character wont have problems if you maintain your vampirism level so that the NPCs wont be able to recognize you.

You don't need to smith or do anything to get decent weapons/armor. Just buy/loot them.
As for the vampirism, I'm fairly certain that once you get to the final stage, NPCs will attack on sight. Perhaps be a werewolf or Mage instead. Or perhaps use one of the 'shacks' you can find around the world as your house? There's one just a short walk from the first village you visit, Riverwood, if you're willing to deal with the lone occupant!

That's good news, I'm reading more about the console to. So I'm getting more and more excited. I'll try the vampire thing later when I'm more experienced I think. I like the idea of Skyrim as a sandbox so I'm goig to use the console to skip the main quest and it's good to know that I don't need to bother with professions. I just need to explore how to skip the main quests/beginning now

You don't need to use console to do that, just stay away from Bleak Falls Barrow. Just like in Oblivion you had to stay away from Weynon Prior.
And it's probably better that way if you feel later in game that you want to kill some dragons.

I'd recommend playing at least the first part of he main quest. It gives you some knowledge about the game and how to play it, and gives you some helpful abilities. If you get bored, simply stop - even the quests that seem urgent can be put off indefinitely! Have fun playing!

For mods, www.skyrimnexus.com

Like the previous posters said, you do not need to use any of the crafting skills to be effective. Then again some people, like myself, do not really start enjoying the game until you have your character built. Chances are that you will be level 45-50, ie a built character, with over 50% of the content remaining anyway. Thus playing the last half of the game with a fully built character.

TES is not just a regular start at level 1, play until level 100, and bam I'm done...game over. Grinding is boring but some call it training. You even see NPC doing it. People practice to get better before going into battle. It is unwise to learn on the fly.

Vamps make the best assassins. I refuse to use the label of thief. I enjoy playing the entire game as a Stage 4 Vamp 24 hrs a day 7 days a week. Never feeding, unless you have the Cannibal perk. It simulates the feeding for RPing and it helps you instead of making you weaker. It actually call for a strategic gameplay. The rewards are very gratifying and it prompts some very interesting and often humorous moments.

Sneak characters are some of the most powerful in the game if played well. You have to cross spec a little for survival though but even then it all fits together nicely. For example a cookie cutter thief / assassin build usually looks like this:

Main skills:
Sneak - Your bread and butter. Max it out and make sure to take the damage multiplier perks
Alchemy - Poisons can make all the difference in tough fights and you get to make your own health potions too. Win win.
One handed / Archery (whichever you prefer) - You need good base damage to make the damage multipliers from the sneak tree worth while.
Illusion - You are going to run into situation where things go horribly wrong and you are caught with your back against the wall. Being a master in Illusion magic will get you out alive by simply calming all enemies in the room, making them fight each other or you can just become invisible and sneak away unharmed for a second shot.

Secondary skills:
Lock picking - No need to take a lot of perks in this but do level it to make locks easier to deal with.
Pickpocket - This one is hard to level initially but gets easier and the rewards are worth it. Being able to sneak up to someone, steal their armour right off their back and then stick a dagger into them is awesome.
Destruction magic - Don't worry, you're not going to throw fireballs around. What you do want however is the magical traps from this skill. Trap damage will depend on skill level so max it out for best results. Onle worry about perks that increase the distance you can place traps.
Speech craft - As a thief you're going to do a lot of selling. If you rebuild the thieves guild you gain access to many extra vendors with decent amounts of coin to pay. Being able to sell off stolen goods to any vendor is a great plus as well. And you'll end up stinking rich in the process.

Also, either join the DB or exterminate them to get access to their armour. It is unarguably the best sneak armour in the game. With the gloves and correct perks in sneak you'll be able to do 30 x the base damage with daggers. That's insta kills most of the time.

Do note, this is just my idea of a standard sneak based build. I do not profess that it is the best, that you should use this and nothing else, or than you can not substitute some skills for others and still have a good build.

I haven't personally tried them but I believe there are already at least a couple of 'reverse vampirism' mods. Basically you need to feed to maintain your powers, rather than feeding to reduce them etc. Just fyi