Jim, I don't think you need to remove the door to make the adjustments Bob is referring to. You need to remove the inside skin to make the door easier to adjust and tweak. If the inside skin is on it keeps the door frame ridge which makes it impossible to tweak or adjust.
As far as the latch goes, the style in your coach is no longer available nor will you be able to find parts for it. Your best bet is to remove the latch assembly, take it to a lock smith and seem if they can get the tumbler to work again.
If not then you'll have to do some cutting and hacking to get a generic replacement latch installed.
Air forums # 1674
1974 20' Argosy Motor Home
1975 24' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels & windows left to sell)