I have an Aspire Acer Desktop

Processor: Intel (R) Pentium (R) Dual CPU E2140 @ 1.6GHZ

Ram: 898mb

Hard Drive: 100gb

Video card: SiS mirage 3

I've always had a mac mini, and really didn't care about updating anything, but now that my crappy 40g hard drive and 512mb ram kills all my chances to play WoW, I'm switching to a PC.

So i want to purchase the cheapest, 2gb ram stick, nvidia 7600 or ati radeon x1600 video and that's probably it.

Can I simply purchase the RAM and Video card, open up the comp, stick them in and have a good time playing WoW, or is it more difficult than that, and is it even worth upping up this comp, should I just buy a new one with better specs? I'm low on cash though, so I figure that just buying the items necessary would be the most cost-efficient.

Sorry if I sound ignorant, I'm quite new to this, but since WOTLK makes it so that I need better specs, I've got to ask.