Drivers door mirror glass

The E36 mirrors are simply clipped into place. The Bentley manual says to gently pry the mirrors off with a small screwdriver. There is a plastic framework hiding behind the glass that the mirror motor moves around when adjusting the mirror. Your new mirror should have clippy things on the back that are the same as what is on the broken mirror.

Thanks Jeff, that's kinda what I was hoping to hear. I did try to prise the old one out but was a bit scared to use too much force in case I broke something vital. I'll give it another try ...

The plastic clips can break if they are very cold. If it's a warm day there shouldn't be a problem, but if it's cold, gently warming the inside of the mirror with a hair dryer will reduce the chances considerably. Wouldn't be a bad idea to warm it anyway as the nylon type plastic used tends to get more brittle with age in any case. Give it a few minutes with the hair dryer to give the plastic a chance to soak up the heat. Mike.

Thanks for the tip, Mike. Sounds like sound advice.