I seen numerous laptop hard drives that failed because they got hot and oxidized the contacts between the controller pcb and the platter/head assy. I suspect at least some of the "freezer fixes" are just due to the contacts contracting and expanding onto non-oxidized surfaces. As for opening the platter/head assy, that's for when the drive is toast and you have nothing to lose. I've heard of people opening them and reassembling them inside a sealed bag or plexiglass box.
Answer to: Is it possible to physically repair an apple ipod harddrive?