frporscheman is right you can take the heater core out whithout removeing the dash. I had a hard time removing the plastic air duct from at the inner side. Also had a hard time finding the screw for the lower vent piece. Other than that it was easy. This is on a 1986 944 that i just got a few months back. The heater core was by-passed so i guessed the core was leaking. After looking at it i don't think it was leaking. I checked the water valve and it works. It had to be by-passed for some reason but how knows.

 

I'm glad it worked out for you.