Having finally completed the main quest as my Nord warrior character, and also experienced the Dawnguard faction quests of the DLC and the Stormcloak war quests for the first time (I have always played for the Imperials prior), I am looking for a new experience within Skyrim as a change of pace from my usual combat-oriented characters who mainly use destruction, magic or perhaps a bit of archery. Since I have seen many people on here playing as an assassin build, I thought I'd give that a go. What skills, race, and quests does everyone recommend me playing?

i think the races are pretty straight forward for assasin class. Wood elf, argonian, Khajiit... that is unless you want to break the mold a bit and use a race that usually doesn't act all sneaky and agile. I like redguards for that purpose.

Skills wise, Sneak is very obvious. If you will be a manipulative sort of character, use your speechcraft skill a lot. Either archery or one-handed for attacks. Alchemy for poisons. Illusion can supplement sneak, or be used for crowd control and general fun

I was thinking of one-handed rather than archery. To me, archery is for a ranger. Daggers are cool! Anyone know where I can obtain some decent daggers early on in the game? I was also going to become a vampire lord as sticking to the night fits the assassin gameplay style and the vampire lord allows me to still go charging in all powerful when needed.

I have a Khajiit assassin, lvl 42 that is a vampire now as well (vanilla) and have used the following.

http://skyrimcalculator.com/#158264

Can't tell you the exact levels of my skills, still have some unspent points as well (3 iirc) though I know pickpocket is maxed, I believe speech is around 80, sneak is 90+, archery is around 40, one handed around 60, alchemy around 80.

health is 360, stam 260 iirc as well. No points in magic.

He's effective at sneaking around, backstabbing the ever loving crap with mehrune's razor, or mace of molag bol if i want their soul. Does not touch illusion, as my poisons are effective for CC and invis. Wasted a point in silent movement in the sneak tree, as you don't need that with shrouded boots you get from DB quest line. Was an oops moment but oh well.

How can I easily level up Illusion so I can get silent casting?

Repeatedly casting Courage on townsfolk. It's a non-hostile spell.

Up to level 30, http://skyrimcalculator.com/#158271

Sound good? What race do people recommend?

Where can I learn courage? Court wizard at whiterun?

He should have a copy of the spell yes.

Muffle on your self continuously works well apparently too?

Yes that does work as well. Especially once you delve into the illusion tree and making the casts cheaper.

For a strong(ish) dagger early on, you can do which is started right in Whiterun.