Yeah, greenmymac is incorrect (unfortunately):
ref.
Put in 2 x 1GB SO-DIMMs and you'll be fine. Make sure to get the correct sticks, ad you'll see there are myriad vendors and brands, some of which are reputable and some of which most definitely aren't. You can play it safe and buy them from Apple, but you'll pay a premium (even more if they install them).
-K