Join Date: Apr 2006
Location: Gainesville/Tampa, FL
Bikes: Trek 1000, two mtbs and working on a fixie for commuting.
Welcome to the forums.
Your best bet would be asking about components and stuff in the mechanics (my mainstay) or commuter sub-forums, though I will note that you don't really *need* high end stuff since at a certain point you are paying more for weight savings. However, if you are set with your retirement and stuff, feel free to spend a lot and help boost the GDP/GNP of wherever you are from. :-)
Knowing how much you want to spend will help us answer your questions because I can give you shifters/derailer/crank for anywhere from $120 to $1200+. You will also need some bike specific tools if you plan on DIY. A picture of your available parts and the bike/frame/whatever is on there will also help. Also, don't ask about SRAM v. Shimano if you come across that. A search through here will tell you why not to and you still won't get an answer - they both are good so either one is fine though I am privy to SRAM for mtbs and Shimano for roadie stuff.
Good luck and have fun.