Leah,
I once got locked in somewhere in Nova Scotia. Wally Kimble got us out by opening the door from the outside. He and I spent a couple hours taking the door apart and fabricating a replacement for a two cent part. We did not have to remove the window. There are adjustments inside that can make the door work better and they are not too complicated, but I don't know how to advise selecting a mechanic.
It did start me thinking about getting in and out without a working door. BJ does not like it, but I frequently leave a window unlocked so I can get in with a ladder. There are three windows I could crawl out, but it would help if someone outside had a ladder and could help me.
Good luck with this. Something as basic as a door seems like it should be reliable.