When I bought this car it was missing the driver's mirror. As it would turn out, she has heated power mirrors. So of course I scoured eBay, forums, and craigslist. I found a few candidates on eBay. This is a great place to find used parts but, sometimes users don't know what they have. Always make sure you know what you need.
When, and if, you have to source a mirror for an E36 make sure you know how many wires your mirror has. In my case, on the drivers side, with heated, power mirrors there are four wires. Power, non-heated have three wires.
Below is my walk through for replacing the driver side mirror on a 98 328i with power, heated mirrors. The whole mirror assembly, not just the glass.
The plastic cover was trouble some to get off. I was afraid I was going to break it. I wasn't sure if I needed to remove the whole door card. You don't need to. Just work carefully. There is one plastic pop tab on the plastic cover at the top corner. This clips into the door frame and holds the plastic cover in place.
I used a plastic putty spreader to pop the top out. With the putty knife at the angle above, I pushed both sides at the angle shown and the plastic clip came out easily.
Once you have the pop clip loose just lift the cover straight up. Up to the sky!
There is also a small U-shaped channel that holds the mirror wires in place.
Under this you will find three 10mm bolts holding the mirror assembly on to the door.
There is a plastic seal between the mirror housing mount and the door frame itself. This keeps the water out I'm sure.
There was also some black foam insulation under the plastic cover. It completely disintegrated when I touched it. If this is important to you then replace this with new as well. The mirrors tend to make wind noise at higher speeds so, I'm assuming this was used to help prevent some of this? Email me if you have more details here.
Take apart old clip.
Plug in new clip.
Push mirror into place. Secure 10mm bolts to some torque specification. I did a normal German spec, Guentight*.
At this point you may want to test the mirror's operation. Just to double check things are looking good.
Slide wiring under the U-channel on the plastic mirror.
Snap the cover back into place and your all finished up. Now go enjoy having a mirror again.
*Good and tight.