RAM is probably the easiest thing to replace in a laptop or a computer. I think you should be capable of doing this. It is also the most cost efficient way of increasing the speed of your computer -- mainly noticeable when having multiple programs open.
You will not lose any data when replacing the RAM. RAM stands for Random Access Memory, and it is wiped clean every time you restart your computer. One reason things run a bit smoother after a restart.
Some advice I want to offer you is that the little tabs that help hold the RAM in the laptop can be a little weak or cheap. So be very careful when you have to pull them apart to get the RAM out. When you pull on them, the RAM should sort of flip up at a 45 degree angle, that's normal. Then just pull the module out. You will insert the RAM the same way, insert at a 45 degree angle and then push down to "snap" them into the delicate plastic tabs I just told you about.
Also, after you install the RAM you want to make sure it is running at the correct speed. I recommend you download and install a simple utility called CPU-Z. You can find it in my signature. Open it up, click on the Memory Tab. In the top box(or somewhere near the top) there should be a box labeled DRAM. What is the frequency say? 533mhz? 400mhz? Etc, Etc. Double that amount, does it equal what you bought? i.e. It says 533mhz so this is correct since I bought RAM rated to run at 1066mhz speed. See?
Are you sure you have bought compatible RAM? You can list the name and model of your computer and I can help you if you are unsure. I can also help you find out what speed RAM you bought if you are unsure.
Let me know, and good luck!
Ask questions if need be.