YOu can open the font by heating it with a hairdryer for about 4-5 mins. Then use a blade to slide in the edge and try to lift from the bottom area near the home button, once you have enough space, use a guitar pick or similar to work the glue free from left and right areas of the home button. Do not force it as you will crack the glass otherwise, once you manage to get the bottom up about five mm you should be able to slowly lift the whole assembly upwards towards the top. Take special care not to rip the wifi flex or digitizer flex which are stil connected at the top end.
The adhesive you need to replace it should be 3M double sided adhesive, 300LSE i think, as sold for the iphone screens. 1 sheet should be more than enough to do the job. Try to clean the old adhesive off as best you can otherwise you will have troubles getting the screen to sit flush.
MAKE SURE YOU SWITCH THE IPOD OFF BEFORE YOU START!!!