I am ordering a 5.5 off of ebay for around $123 (New battery and new 80 gig hdd). How hard is it to open the 'enhanced ipod video'?
I upgraded the hard drive and battery in my iPod 5.0 Video a few months back. Structurally, I believe it is identical with yours with only minor differences in electronics or firmware. I found it surprisingly easy to crack open following the iFixit guide. Nothing broke en route and everything worked first time I powered it up afterwards and reliably since.
I only needed a spudger to prise a gap between the facia and the metal back after which a couple of guitar picks strategically placed gently separated the two.
Only bum note is that the battery I sourced, whilst nominally of a larger capacity than the one it replaced, does not seem to be giving anything like the battery life I expected and noticeably less than the one my iPod Classic can muster. It might pay to not skimp on that and check reviews before buying.