If it was me I would cut the access door, all the info is in the technical archive, should have been done from the factory IMO, easy enough to make the piece cut out a bit bigger and, make a rubber gasket and secure with self tappers.
A woodwork vice would be safer, clamp it lightly and heat with a heatgun, clamping tighter as it softens, protect it from marking with two pieces of silicone like soldering mat material, then leave it clamped until it cools completely, just an idea.
Don't think that's gonna work, the glass is encased in plastic with the element built in, it attaches with a clip on the back that, usually breaks when prising off the old one, if you get the correct one be sure to order a clip as well.
Island have heated ones, I replaced mine a few years ago now, about a tenner plus vat but, they're £13.99 now.
edit, just had another look RH ones are £16.50, for some reason.
Optikool glass has a green tint, supposed to stop the heat of the sun, can't say I ever noticed any difference but, in hot weather the aircon was on anyway.