Seeing that I'm about to embark on my PC Skyrim adventures now I've got my new PC please could you experienced modders give me advice on starting out? Just to let you know I'll be doing HEAVY DUTY modding, so I'll need advice on the best programs needed for ambitious modding. I understand Nexus Mod Manager is a good one, or has something better come out since? Also, does Mod Manager work with mods from elsewhere, like Steam?

Sounds like by modding you just mean using mods, not creating them, right?

NexusModManager should be the only mod manager you need, and I -think- it works with steam. I get all my mods from the Nexus, so I can't say 100%.