I once read a thread where a guy cut a 2" x 4" hole in the steel dash structure to change the actuator.
Not my recommendation.
I removed the dash to change mine but there has been one or two that were able to change from under the dash. Afterall, the actuator does live on the heater core cover so if you can get that off, you can replace it. The problem is that there'* not a lot of room up there. I scratched the hell out of my arm and hand while swapping the HVAC programmer in the 93. There'* one electrical connector directly from the programmer to the actuator and it'* up there.
If I had to do it again, I'd remove the dash but it is possible to do without.