I'm sure that as always, I'll get run out of this thread on a rail, but I'll say it anyway: I'd take the trailer home, and fix what needs fixing myself. Even if I had to buy the window myself. They are only a few hundred dollars.
Because here is what is going to likely happen. They are going to assign the window replacement to the 19 year old high school dropout in the shop. Then you will find out a few months later it's leaking when it rains. Etc.
Take it. Fix it. Enjoy it. Fix it some more. Repeat.
As I always say: "some assembly required". If you are not on board with that idea, then RV ownership is going to be a frustrating hobby for you.