Is it possible to replace the mirror-glass in the OEM side-view mirrors ?
Does the gasket-retainer get destroyed in removing mirror pane ?
Who sells new mirror panes and correct gasket-seal-retainers ?
Is there a trick or known procedure to remove the pane ?

The black trim piece will come out. easy if the mirror is broke. Just need to start one small area and gently pull it out. It has a small groove the the metal edge rests in. I made an 1/8" masonite pattern and use that to cut and grind double strength (1/8") mirror.

Auto Atlanta Mirror (Type in a search for "mirror glass")

You can buy it new at AA!

Easy. Remove black trim as mentioed above. Take mirror to local glass shop (not AA) FDLFBFG.

+1 Fifteen bucks for two pieces, one for each side.

I have replaced several with no problems. I have several extra parts if you break something while trying to remove.

My 'mirror guy' cut one for $8 bucks. He got it right on the second try!
The black frame bit is key.. the clear plastic thing behind it should be snug around the glass. It then goes back together nicely. My clear plastic thingy was split but I taped it with some metal tape. Everything looks good now.
also tighten the bolt 'while you are in there'