GOO = Weight = Bad
You were overweight by 40lbs or so on the scales at Miller so 2-3 lbs of goo needed not be replaced.
Replacing the fender on a race car is not hard since the replacement need not be aligned just perfectly. So the hardest part will be FIND all the bolts under all the goo.
The alternative is hammering and bondo. I did that to my left front fender rather than replacing it. I only have 1 spare (1 944 and 2 924S parts cars leaves few spare 944 fenders) and as such I like to repair as much as possible since if that fender gets really crunched then I will need a replacement. I forgot how bad the fender got hit. The metal is pretty easy to bend back even on the car since you can get to the back side pretty easy.