From one ARF newb to another:
1) Check around the sticky post at the top of this forum: "THE IMPORTANT THREADS AND INFO", especially the thread of acronyms and abbreviations.
2) To toss out a few names: Bushmaster, Rock River Arms, CMMG, etc.
3) Depends entirely on what you want. Different kinds of upper receiver (A1 "Vietnam" style, A2, A3 flat-top, etc), different barrel lengths and profiles, different kinds of stocks, different types of forearms, grips, etc. To get a really general overview, check out any of the AR15.com picture threads. They just started #11, and #10 is still floating around a few pages down. All of those have 40 pages of pics and comments on rifles owned by forum members.
If you just want to shoot stuff for kicks, and want an "Everyman" AR, take a look at an A3 upper (detachable carry handle), collapsible stock, 16" M4 profile barrel. An off-the-shelf example would be the Bushmaster Patrolman rifle, currently listed at $799 at www.cdnninvestments.com
The Patrolman (and similar models) are great because you can easily add optics or railed handguards, handy length, not too heavy, adjustable stock easily accomodates your build. And remember, it's pretty darn easy to change most of those things around on any AR.
I went through a process similar to yours recently, and was captivated by the "Retro" threads currently running on this forum. I ended up building a quasi-faithful reproduction of the Vietnam era Colt 605 rifle, all from new parts. Cost me about $750 overall. I chose that model because I wanted something a little different than the rest, and wasn't concerned about adding high-speed/low-drag optics, lights, lasers, etc. If you want a really simple AR with Vietnam-era stylings, those can be a really fun project, with minimal effort and often far less expense than the whiz-bang modern stuff. I like old school, despite being a 25 year old.
In four months, you can learn enough about ARs on this forum, so that it'll crowd out all the other info in your brain (HINT: write down your name and address on a laminated card, so you at least won't lose those).
Good luck in your AR future, -MV