I can do it in my Imperial Coupes but I’m guessing there’s a little more room to work.
I do remove all but one or maybe two screws holding the regulator and loosen the other(s) to the last couple of threads to make it easier to remove the 3 screws holding the motor to the regulator. This is a good opportunity to clean old grease off of the moving parts and add new.
I'd go ahead and take out the motor and regulator. Check other components and make sure everything is in good condition. Rebuild your current motor if you can. Any new one will be a piece of junk. Lube everything well when reassembling. And apply some kind of sound deadener with the plastic sheet behind the door panel. I have large arms and sausage fingers so I hate working inside of doors. So when inside, I don't want to go in again if I can help it. Also, taping the window in the up position makes things easier.