Yes you will need a new gasket it is about $80-$90 from the dealer. As for removing it I have yet to do this same repair on mine, I am waiting for winter break. But my dad has removed one from my parts car and he said it was simple. I know you need to pull down the interor panals to disconnect the connections for the heater. I think after that you can just push the rear window out but I am not 100% sure.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200