To answer your questions:
1. Best for your $$$ would be something like the Gillet Ball Buster Turbo. Also known as the FatShaft turbo or the USA Turbo. They are all about the same.
2. If you have supporting mods (intake, exhaust, programmer, mapfooler, bigoil, injectors etc.) the H2E and the H2E(modified) are the best single turbo setups. There are also twin turbo setups that can produce upward of 60psi and get you over 500-600hp AT THE WHEELS.
3. Before you start looking at a new turbo, I would drop $1000-1500 on gauges (EGT, Boost, and TransTemp), a 6 position chip, a 4" or 5" exhaust, and a tymar intake system. After that, your going to be seeing 24+ PSI of boost on the stock turbo and you need a mapfooler (electrical or mechanical). Your also going to be experiancing A LOT of compressor surge. If your poor, like me, you can buy some upgrades for your stock turbo like a wicked wheel (compressor wheel), an ATS compressor housing, larger exhaust housing, EBPV and wastegate delete etc. Then on to Big-Oil (dual HPOPs) and onto better fuel injectors.
I think that about covers all of the basics. A little searching and question asking here on the beloved .org will do you well.
Also, if you could, put some of your truck's stats in your signature so that we can help you out better. You may use mine as a guide.