The HG rarely go on these motors. Usually it's the LIM gaskets that let go. There are also coolant passages for the throttle body. Conventional green coolant is fine for these cars as long as the old Dex has been completely flushed from the system beforehand. I run green in both my 95 Bonne and 00 GPGT and have had no issues.
Good on you for changing the oil several times before driving it again. Don't want any spun bearings on the lower end due to coolant in the oil. When you fix the source of the leak just use some cheap oil/filters between changes to clean the system. When you are sure there isn't any coolant there fill it up with a good premium oil/filter and you should be good to go.
