Fiberglass fenders- junk

That's a hard question to answer. If you were to take it to a shop for an estimate I think you'd find that most shops wouldn't want to touch it.

That upper door gap does look like you could grind off some to gain clearance but it also appears to need to be built back up on that corner.

If it will be too flimsy overall, then you're looking at possibly having to add another layer of fiberglass to the inside of the whole thing.

Whether or not you can get the body lines to line up is probably going to be the biggest issue. Are you going to have to reinforce it to get it to maintain the correct shape?

With all of the work needed to make it satisfactory you're going to have a fair amount of time invested. It may not be impossible but definitely going to be a lot of work.

I don't imagine they'd ever take it back once you start trying to repair it either. Before I'd start on it (if you decide to) I'd be very careful about assessing whether or not you believe you can get it right. It's really hard to make that call looking at the pictures. - And I think you should take a LOT of pictures of each of the problem areas as you try to fix them. I'd also want some kind of documentation of what type of restitution they're willing to make.