73 Is a pain to work on because the glass is riveted in and usually has glue and some cars have an additional side crash bar inside the door that gets in the way of getting at the regulator.
I think you can swap a 71,72 regulator in but you have to modify the glass to put bolts through the glass. not 100% sure.
either way panel has to come off.
which means pulling the glued cover off the regulator to get at the screw.
take the handle off and the chrome cover. Now just to be sure, look at the back of the window handle and make sure the splines are not stripped out.
unscrewing the lower plastic cup that is behind the door latch. 2 screws.
that should release the lower door handle as well.
then popping the panel out, watch for the spring that is behind the window crank handle. (this just pushes the door panel cover out to meet the window crank handle so it looks nice.
pop the bottom of the panel out first then work your way up to the top the top of the panel with the window whiskers is sort of hung over the door so lift it up to get it off the door frame.
then pull down the watershed paper/film
and you can see inside the door.
the more options your car has like door speakers, electric windows, makes it more a pain in the butt to get inside.
from there you can see what broke.