Your model no is incomplete..... if the light is in the right rear corner or the centre of the roof it has spring steel tags that hold it in place as you push it in the hole. Easiest way to release tags is to remove the oven and and get to the other side of the light fitting and force them to retract. Quickest way is to wreck the fitting by forcing the tags from inside the oven, as you are replacing it it doesn't matter. ISOLATE FROM POWER SUPPLY OF COURSE BEFORE WORKING ON IT>
Kenjo
January 2015