Blend door actuator replacement guide

[Young1]

I have searched the forum, the stickies, the web and have come up zilch on how to replace this on a 1991. What I have learned is that the actuator is on top of the AC/Heater box at the base of the windshield. I assume the General assembled the system before installing the windshield.
I have examined the blend door through the blower resistor opening. It travels at it should but pops when hitting its limit like the gear is stripped. The cabin was receiving a moist cool feeling and I suspect the blend door is not staying shut. I jammed some foam in the box to hold it shut and now it blows cold. The refrigerant system has been checked and is OK. No codes either in the climate control module.
So ?? who has replaced this actuator successfully and can be my guide? BTW my original dash has no cracks and I wish to keep it that way.
PS there is a YouTube video of a this done on a 94 but later models have the actuator on the bottom of the box making it somewhat simpler bu non applicable for me.

[secondchance]

What makes you think blend door actuator location is different between 91 and 94?
Actuator seems to be same part for 91 and 94.
YouTube you saw probably is this

https://m.youtube.com/watch?v=l9wTpK6nBZA

and applicable to 91 as well.
In any case, removing the dash is not that difficult. Just time consuming.

Edit - I saw a post on Corvetteforum where later cars the actuator was moved to the bottom for ease of service. I still cannot picture how that would be possible...