1. cannot upgrade the graphics. even service center cannot help u. the GPU is soldered to the motherboard..meaning if u wanna change the GPU u have to change the whole motherboard...including the CPU n such. dats y u should get AppleCare Protection Plan, cuz if GPU rosak, the whole thing have to change

2. i would recommend the brand Crucial but its very hard to get in malaysia. those normal kingston KVR, mushkin, corsair works as well. just make sure its this spec: DDR3, 1066 (or 1067) Mhz, SODIMM.
most notebook hdd's in the market are compatible. make sure its 2.5" SATA, 9mm (most under 500gb are 9mm btw...if u're buying >500gb better check 1st). price range uhh depends on how big u want ofcoz... 160gb is around rm170 and 500gb around rm280. as u can see 500gb has a very good value now... 56 cents per gb

for 500gb i'd recommend WD scorpio blue and hitachi 5k500. for 320gb, u can consider the faster 7200rpm models