Has anyone had to replace a heater core on a TB/Envoy yet?

I have a nasty coolant smell and moisture (on the windshield and side glass) coming out of right side defroster and dash vents. There is a fair amount of coolant in the foam insulation for the heater core and A/C lines in the passenger side footwell but no wet carpet.

The Haynes manual shows a very involved repair including removing the dash, instrument panel and steering wheel(!) and my GMC dealer wants $925 plus tax!

Do the engineers who design this stuff ever think that someone may actually have to repair it someday?!

Any feedback would be appreciated and thanks.