I bought my D3 with this problem thinking that it was an easy fix. It’s not. The entire sunroof unit (or “cartridge”) needs to be replaced because the guides are part of the unit. My indie mechanic found 3 or 4 consecutive units at salvage yards and each also had the broken guides. By the time they found one with unbroken guides, I had decided to buy a new replacement unit. The take-away is that you should make sure the person searching for a used replacement unit knows how to check the guides before taking it out of the donor car. Good luck.