By recommendation do you mean types of RAM? Because pretty much any PC2-5300 SODIMM (the SODIMM means it fits the laptop ram slots) ram will fit in your notebook. The ram should be hidden under a panel somewhere on the bottom of your notebook. Switching out ram nowadays is pretty easy.
For example: http://www.newegg.com/Product/Product.aspx?Item=N82E16820145193
would be an option.
Keep in mind that if you're running a 32 bit operating system, you'll only see about 3.25-3.5 gigs of that ram, because the rest can't be used unless you have a 64 bit operating system.