Tony, 
My .02,
You will hear a lot about the famous leaking head gaskets if you hang
around this list awhile.
After learning the hard way about this with my '84 GL, I have changed the
coolant every year in my '87 GL and at 155k have never had any leaks. I've
used non-phosphate brand 'Sierra' now for four years.
Cheers,
Jess Lopatynski
87 GL
85 GTI
89 911 Targa