One problem related to sun roof has been reported for the 2000 GMC Envoy. The most recently reported issues are listed below.
With the factory installed sunroof the rear compartment has no lighting without turning on the entire cab lighting. This proves to be a glare hazard at night when the passengers in the rear need individual lighting. Models without sunroofs have individual lighting for the rear passengers but not the models with. The manufacturer has no interest in making any changes to the 1999 or 2000 model years by offering a light kit accesory for the rear occupents.