I hear this complaint quite often.Not a terribly difficult resolution, but it does require some getting dirty.

First, a make a trip to your local paint dealer and purchase a stripper suitable for use on fiberglass. I use a water rinseable stripper. A big concern I found the hard way. If the trim around the glass is styrofoam, DO NOT chemically strip the door. If not, proceed with the stripping. Once stripped, stain and varnish according to the original instructions. One important thing people tend to miss is maintenance. These doors must be varnished once per year, or the finish will fail.