I'm pretty sure you just pop it in the back side, very easy to do.
Before spending the $$ I would use the task manager to check just how much of your RAM you are using when recording, there is a good chance you might not even need it. I have found the stock 128 MB to be fine, but all my picturebook does is record (24/48 over USB), so I don't really ever run multiple programs at the same time. Of course depending on your needs maybe the extra RAM will do you good.
Take care,
Ben