91 Olds 88 Royale

I did a search, but only found limited results.

I was converting and charging my GFs mom's AC, but realized it never worked for her since she got the car. Problem is, I can hear the blower running, but nothing comes out of the vents. So I pulled off the center panel to expose the vents. Inside one of the vents was a flapper of some sort that I surmised controls air flow to the dash vents. It was covered in muck. Is there a way to clean this? And does anyone think this is the problem? Or could it be a vacuum hose problem?

Also, when converting to r134, does anyone have a picture or description of where the low pressure valve is that needs to be replaced? I'm pretty sure I found it, but it doesn't seem to unscrew like the recharge kit illustrates.

Thanks from a newbie!

John