I have had problems with removing the glass cover of the lamp in my oven before, I bought one of these removal tools and got it out with minor difficulty
Then the next time the lamp blew I could *NOT* get it out again, I've had a few attempts every few months when it annoys me, but yesterday I decided it was going to come out one way or another ...
Took the door and shelves off, took the oven out of the housing, took the top and back off, rested it on its back to get a better 'purchase' on it, dribbled washing up liquid around the glass cover, not budging, poured some more around it, left it overnight and this morning SUCCESS!
The cover is chunky glass (a bit like one of those GU ramekins) and screws into a metal socket, my oven doesn't get much in the way of greasy roasting, it's pretty much just for baking bread, croissants and oven chips.
So what should I smear on the cover to try and stop it getting stuck again? I've got some food-safe grease that I use on the coffee machine.