Are you sure all the reinforcements are in the nose. If its sagged out of shape, theres really no good way to fix it. Your prob better off finding a good used one with all the reinforcements included. Heating it will more than likely make it worse. There are places that will restore it, but that will cost more. I had an 84 corvette in here that had both covers, front and rear in really bad shape because it had no reinforcements. I actually think 86 (first C4) did not have them at all. We replaced both of them with fiberglass aftermarket ones that were cheaper than the original replacements.
The roof rot is typical Fiero. There was another thread with the same issue just a week or so ago where I described how I fix them. There of course is more than 1 way

It comes from water seaping in around the seal and soaking into the matting in the roof material.
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