The urge to mod is strong with this one...
OP, Bob has it exactly right. I know you're excited, but you need to drive your truck and get to know it before you think about mods, and you need to do a LOT of research on exactly what mods to do before you do them. It'd be nice if all your questions could be answered in a couple of forum posts, but the fact is the real world doesn't work like that. If you start modding right now, you'll be wasting time and money.
Go get your truck dirty. Get stuck, get pulled out, get high centered, get rescued, learn what you (not the truck) can do and what you can't, and then start thinking about what more you need.
If you absolutely need to buy stuff for your truck right now (and we all understand that urge

), invest in a good set of AT tires, maybe some nice shocks, and if you're going to get in the rocks a good set of sliders and a rear bumper are practically mandatory. Start with that. Have fun!