Half of my ceiling inside is bad. Obviously I have to rip it out. My question is there anyway to match the part I take out to the half that is good or should I just take it all down and start fresh. I am already tearing the walls out. I would rather not take on more work than I have to. Any ideas?

I would think that you would have to take down all the interior ceiling. You may find additional water dammage. Thay way when you repair your ceiling will look all the same. When we did or renovation we found the the water came in one spot and traveled great distances. You will be able to put in better ,more insulation. No fast easy way to do these repairs. When you get done you will have a correctly repaired trailer/new looking.