Welcome!! Your best bet is going to be to parse out your questions into the appropriate sub-forums on here. That way people can see what you're asking about, versus one giant batch of questions. Just don't litter the forum with 50 posts either.
My best question for you to think about is: What will this vehicle be doing? My answers might differ it's just your DD and you drive 5 miles a day to work on city streets vs if you want to build a hard-core off-road rig with the truck.
My suggestion for first things to do: Get it back up to factory standards. You mentioned shocks, it's time to address those. I prefer Bilstein over Rancho, but they're more expensive. Make sure the suspension is all up to spec, your tires are in good shape, give it some new plugs, fresh fluids all around, and just make sure it's going to be a good reliable driver. Check out this forum and see what common problems are and how to fix them.
If you're new to wrenching and working on cars, go to YouTube and check out Roadkill and HotRod Garage, Dirt Every Day on the Motor Trend channel. There are a ton of cool projects, great ideas, and just funny stuff going on in that. Check out other sites and find out what you're passionate about and start working on it. Maybe you'll find that the Tahoe is a great DD, but you really want to find a CJ-5 and go out in the desert with your buddies, or something. Do some exploring. I've been watching automotive TV since I was a kid, (back when we still had to watch commercials!) and it's what's fueled my passion for cars, as well as my knowledge.
As far as mods go, I wouldn't worry about turbos, cams, gears, etc if your first time wrenching on a vehicle was installing the K&N intake. Do the little appearance things you want to do, fix what breaks, and enjoy the vehicle for a while as-is, and as your skills and comfort level grows, tackle bigger projects, like the exhaust.
Finally, it may be cool to go on here and see that so and so did a supercharger, or this or that, but understand that their situation is probably different than yours, and don't run a giant credit card bill up to make a cool truck that your friends like. Make the truck cool, but make sure you're focusing on things like maybe finishing college, getting a good career started, buying a house, family, etc. It's fun to have a cool vehicle, but if you're scrimping gas money because you wasted it on rims or a paint job, doesn't make it that much fun anymore.