You should check with RayMarine. They have a repair service, while a bit on the expensive side, you essentially get a new unit.
One of the members here a few years ago - cannot remember who - twisted the connector off the back of his fishfinder, chartplotter, or something.
After looking to replace the connector, he finally just sent it in to the RayMarine repair facility. His unit was out of warranty, and I think they had a flat rate repair fee - I dunno, $250, something like that.
But he essentially got back a new, or at least, completely refurbished unit.
If you are gonna try something like removing and replacing the glass, which might end in disaster - might just as well have it repaired by RayMarine.
RayMarine makes or recommends a screen cleaner, but it might be too late for that:
http://www.raymarine.com/highlight.aspx?site=1§ion=2&page=122&highlight=2355