Kevman

hello I have a 1995 C1500 has heater only bought it used found that the heat air mix control was not hooked up looked futher into it and discovered the back (closest to the front of the vechicle all the way on top) arm with the spring in it had the plactic pin out or the hole the opens and closes the vent. On further inspection the same vent is out of the holder on the passenger side. I took the lower box screws out reached my arm up inside and can feel the hole the end of the vent that has the pin on it is supposed to go.
My questions are what holds the passenger side of the vent in, I know I am missing a part that holds the switch control on and am wondering if that is all I need?
If the the vent is broke inside how do I remove the air distribution box so I can replace it? According to the Chevy parts list on my truck the vent it's self is not replaceable you have to replace the entire distribution box.
Thank you in advance to anyone who can help. Kevman