On most laptops replacing RAM is pretty easy. You usually undo a screw or two and either pop off a small plate on the bottom or pop off the keyboard.

So long as you stick with a major brand of RAM, you should be ok. I usually recommend Kingston or Crucial. Patriot, Corsair, Mushkin, OCZ are other good brands. If you're at all uncertain about what to get, I'd go over to http://www.crucial.com/ and use their website to figure out what you need. If you use their "Memory Advisor" tool they'll guarantee compatibility, they have a lifetime warranty on their memory products, and they have free ground shipping and cheap expedited shipping.