Depends on your time and what its worth. I have had fiberglass fenders on all four corners of mine for 13 years with out problems. One thing I would do different is have the underside of them heavily coated with bed liner or undercoating. Rock "star" marks are in the front fenders from being thrown off the tires. I suspect steel may do the same thing, but never having them I wouldn't know. I didn't want to look for steel fenders for years, so that was my reason, and at the time, they were only $125 each. I couldn't have fixed mine for that. In all the years I have had mine at shows or meetings, no one has ever come along and said anything about fiberglass, most of the time I point it out to show the wider rear fenders. And for over all value of the truck, I doubt it makes much difference.
Joe