It only has two slots, so you can't use your existing ram (2 X 2gb). 

Sites like crucial.com lets you know what kind and type of ram you can buy. 

I got..CORSAIR 8GB (2 x 4GB) 204-Pin DDR3 SO-DIMM DDR3 1066 (PC3 8500) Laptop Memory Model CM3X8GSDKIT1066 G from newegg.com only because it was kind of cheap. $59.99. 

It is very simple to change. Here is a youtube video of it http://www.youtube.com/watch?v=KckvTQh658M 

You can always resell your old ram on ebay.

If you do a search of upgrading 4gb to 8 gb of ram in m11x, some people say you won't notice a lot of difference in general use or games.  

Thank you for your reply, this is very helpful!

I heard the same things about getting more RAM being unnecessary which is why I only got the 4 gigs when I bought the laptop. However I play games like Civilization IV and V and noticed that my RAM usage was over 90% while playing longer, larger games so that's why I'm looking into upgrading.

Again, thanks very much for your help.

And one additional question: could I simply buy one 4 gig RAM and keep one of the current 2 gigs in so I can have only 6 gigs? I think 8 would be a bit too much. I apologize if the answer is obvious, I have never done this before and would like to be as careful and certain as possible.

Thank you.

You can mix and match to get 6 gb of ram.... 

But I think this messes with your Ram Speed. It is suppose to run in dual channel so ram sizes should match for all your ram to run at ideal speeds.

So I think if you mix a 2 gig with 4 gig.... 2 gig from each stick will run in dual channel and the left over will run in single channel (?).. BUT i'm not 100% sure. Anybody else know or mix ram? 

With only 2 sockets ... exactly identical DIMMs must be installed in both sockets to keep the memory running in "dual channel" mode.