The 5 R's are the way forward for most problems, and I don't know if removing the battery is going to fix it beyond the 5 R's. It may. Here's how you can open the case.
I had a 4th gen 40GB model. Having had too much free shampoo on a flight, I dropped the bloody thing out of my shirt pocket into a bog bowl of urine and formaldehyde. I was well impressed, but too pissed to do much other than flush the blue stuff out of it. Having sobered up, I read up on the internet, and cracked on with opening it. I used a v sharp chef's knife, and worked it into the join between the metal and plastic (at a corner). As I made progress along that joint, eventually, one corner will "pop", ever so gently. You can then prise up the rest of that side. I then used a sliver of old credit card to chock that side open, and repeated the process on the other side. Eventually, all four of the engagement detents will pop loose.
BE VERY CAREFUL WITH THE KNIFE!!! A large amount of force was necessary to pop the detents, and had the knife jumped out of the slot, it would have been very easy to ruin my piano practice.
It turned out my LCD was the only casualty of this urine-soaked-Ipod episode, but that pretty much makes it BER. One times 1043 later, I had a shiny new color one.
Moral of story. Do not put Ipod in shirt pocket. Good Luck!