What kind of file? Music can be mp3, aac, wav... and iTunes can help you produce and sync those. If video is what you are looking to do there are many programs that help encode a file to the ipod's specs like Handbrake and the defunct VisualHub. Give us more details about what you want to do.
iFixit sells a replacement trackpad with the upper case: MacBook Pro 15" (Model A1226) Upper Case It is listed as "moderate" difficulty. In my experience, if you are careful and take your time, sort screws as you remove them, you'll be fine. Cheers!