What kind of computer did you buy? Windows or Mac?
If it is a Mac, you can hook the two computers together via firewire and insert the OSX setup disk in your new computer. It will prompt you for some info and automatically copy all your mp3s, docs, setting, bookmarks and anything else in your user directory to the new computer.
If you're using windows, it's not quite that simple, but still doable. Go into iTunes and find the location you store the files (under preferences), browse to that directory in explorer and you should then be able to copy them using one of the methods people listed above.