Hold button is broken? How to fix?

Ok, well I bought an iPod 3rd generation on ebay and the hold button was not working. Well I opened it up, and it turns out the little black switch thing that sticks up out of the little silver box bascially fell off when I touched it. So now there is nothing for the hold button to catch on to in order for the switch to work. How would I replace something like this? Would I have to replace the whole green flat part that it is sottered to? How hard is this? I mean I guess its not a real big deal, but because the buttons are so sensitive, it is realy hard to not have a hold switch because everytime my hand comes near it, it changes the song. Are there any cases that could help with out fixing the hold switch? Advice please???