Dropped iPod classic 7G had cracked screen. Decided to upgrade while fixing, so I replaced the LCD and swapped in a Toshiba 240gb drive. Thicker drive necessitated using a thicker back, so I had to replace the back too.
Piece of cake. As usual, the hardest part was getting the case open. Was done in 20 minutes.
Unless your screen is already cracked, keep away from the screen as much as possible when opening the case. Work in the middle of the longer-sides first...then get the bottom going. Go SLOWLY!