I just finished a 300TD that I replaced the fenders on. I had one used OE fender and one "new" aftermarket fender. The OE fender took about 1/2 hour to fit to the car and the aftermarket fender took about 5.5 hours.
They both look better than the rusted out fenders that were there, but the aftermarket fender isn't perfect. The upper rear corner where it meets the "A Pillar" isn't shaped the same as the OE fender. It could have been reworked, but I was on a time and $$$ budget.
Here's the thread with pics:
Keeping another 123 on the road