iPod Bringing my 4th Generation click-wheel Back to life!

Bought this ipod around 2004. Used it consistantly for about 3 years, no problems. Then it wouldn't power on in 07. Then I bought an iPhone and haven't used it since.

However I WANT it again for the car as it holds 20Gigs, (well 18.5- the beauty of apple) I tried turning it on at the weekend and I got the unhappy face, which is generally bad news, or hardware issue, I'm lead to believe.

http://www.methodshop.com/gadgets/ipodsupport/ipodicons/ipod-sad3.jpg

I tried to open it to perform what seemed like a crazy idea: placing a folded business card on top of the blue sponge, as it loses pressure over time. Eventually I gave up, for my own sanity, as I could not open it!

However, I popped it into the wall charger and it worked, I was over the moon happy! I let it charge for a good 8-10 hours and when I took it out, it wouldn't work. I came to the conclusion that it was a battery issue. It only worked in the wall charger. It didn't even work when hooked upto my macbook.

It generally works fine, when in the charger, except for the odd time when I get this screen:

http://www.unet.univie.ac.at/~a9126300/ipod/ipod_err.jpg

Any ideas? If I buy a new battery should it fix all issues?

Thanks in advance

Forgot to mention: I never get the SAD FACE anymore. Only the file exclamation mark occasionally. I presume I must have done something when I tried to open it?

I reckon I'll just buy a new battery off ebay and see how it goes. any tips on opening that bad boy? Ive watched all the youtube vids and nothing worked, flat screw drived, guitar pic, knives, RIEN!??

Any tips on buying a battery on ebay? They all claim to be CE approved, but I'm sure there are a few dodgy ones out there. Would an extended one like this do the job?

http://cgi.ebay.co.uk/Apple-ipod-4t...tZUK_CE_MP3Access_RL?hash=item562d74e5dd#shId