Removing the stuck down battery was made easy by warming the back case. i did this warming plate beside my stove but similar techniques for screen replacement could be employed!
I was given a 3gs that had fallen in the toilet. (clean bowl) afterwards it only came on when it was plugged in and you could get it into restore mode but that was it. I felt it worth a punt to get a battery of the flea bay and have a go. I found putting the mother board back in a fiddle but i did it and tested the old battery. it was completely dead. I then replaced it and hay presto a working 3GS for the price of a battery. AWESOME! thanks FIXIT.
there are loads of people trying to sell 3G and 3GS models on Flea bay in a similar state as this one but not sure if the fix would be this simple!