Buying a New PC

I'm buying a new PC for the first time in several years (I just moved to a new country, and it would have been more expensive than it was worth to bring my PC with me.), and I'm finding the experience a little daunting. I have a rough idea of what I want, and I like to think I'm fairly computer literate, but there are a few things that just baffle me; namely, the processor chip and the graphics card. I'm able to understand and appraise every other component of a computer, but these two may as well be written in French as far as I'm concerned (I don't speak French by the way). Is there a rule of thumb you can use to compare processors, or do you just have to really look into each processor individually? And the same question for graphics cards.

Also, if anybody can recommend any good deals going on PCs at the moment, I would really appreciate it. I'm looking to spend around $500, but I'm prepared to go as high as $1,000. I want at least 1GB of RAM; I'm not particularly fussed about ROM, though 200GB+ would be nice, and I'd like to be able to play recent games at medium resolution on the machine, but that's not a huge priority. The PC will mainly be used for college work, office work, etc. If anybody knows of any good, or great, deals that are running at the moment, then please do let me know, even if the PC in question doesn't quite meet the specs listed above. Oh, and the availability of a monthly payment plan would be a definite plus.