painting a fiberglass door

I have a fiberglass entry door that was installed about 5 years ago, at the same time my house was being painted. The paint on the house has held up beautifully, but the door looks just terrible.
I'm sure it was not prepared correctly, and I know it was painted with an oil base paint. Now its full of mildew in all the tiny "wood grain" crevices and the paint itself is chipping and peeling.
Does anyone know if I can sand this door, and go back to square one and prep it correctly to better receive the paint?
Its a double door with full length leaded glass inserts so the sanding would be complicated, but if there is no other way I would try to find someone to do the work.
My other choice would be to clean it with a good mildew cleaner and then repaint it. (which I can do myself). Any advice and/or suggestions are respectfully appreciated...
:)
HB