Hard Drive Replacement

Ipod Classic 120GB 7th (im think) Gen

Model Number: MB565ll

Hello my Ipod has now ran its course so im looking into finding a new hard drive and battery to replace my old one. This is my first time replacing anything for my ipod, so i don't really have to much knowledge as to what to look for when it comes to hard drives. is it also possible to upgrade my ipod to a 240gb if so how much does that usually cost along with who would be able to do this. thanks