2x512mb.I wouldn't say HUGE. But it should be noticable. How much ram do you have now?
I'm new to laptops, so I dont know too much. I think it is a ATA-6 and if it is I was thinking of using this: http://www.newegg.com/Product/Product.aspx?Item=N82E16822146052Don't see why not.
I looked it up some more- I have the Hitachi Travelstar 4k120. It runs ATA-7, while everything else is ATA-6. So I know I'm going to upgrade that.Or there is a panel on the bottom that pops off and then you pull up the hard drive. Take it out and check what kind of HDD it is. I would guess Sata.
I don't understand your memory question.
should be able to. Although I would reccomend getting 2 1gb stick to run dual channel.