Can a Fiberglass dash be re-shaped?

You can surely repair the fiberglass easy. Instead of heating the fiberglass, Better to remove leather and cut the fiberglass and reshape with fiberglass cloth and resin.(fiberglass repair kit). You can make a simple mold if needed out of cardboard, hot glue, cover with wax paper. When FG is just about set up(not rock hard) you remove the cardboard etc. Or you can reshape with FG and use bondo to get final shape. FG is needed for some strength. When bonding new FG to old FG, sand the area to be bonded on old FG for clean surface.

 

You might get lucky with an iron (you know the things used to make shirts look good on the hanger.....)

 

I have experience repairing fiberglass boats, if after the leather is removed the fiberglass is still warped I think that it would be better to cut off the piece that is warped and cut it at such an angle to correct the warping and then reattach the piece. By properly preparing the surface, filleting the joints and using a good epoxy resin (like West System) the repair would be permanent. I don't think heating the piece under load would permanently correct the issue.

 

Normally there is a padding underneath the leather or vinyl.

Agree that cutting the deformed sections out (or segmenting them as they do to wood to steam bend it) is the way forward.

The padding is what lets the final trim surface "look smooth".
Trim Shop should be able to handle it!!