Does a new touch panel work right when you attach ribbon cable?

I am trying to put a front panel assembly on an 2g iPod touch. I have the old one off and the new one is ready. My question is this: with the new panel laying beside the unit, if I attach the ribbon cable should I expect the new touch screen to immediately operate? Or will I ahve to snap the new assembly on to the frame to see whether it works or not? I just want to know if I can test the functionality of the new assembly before i snap it in because I am not likely to get it back out in one piece again.

Any advice appreciated