BRAKIE I'll tell you straight up, I have some cars I was half afraid to change out couplers because of the minute detail.
When I get a new house car, I generally remove the floor/underframe assembly and stick the body on one of those spring-loaded paint holders so I can weather it (powdered charcoal) and then spray it with flat finish. I did that with one of the new Tangent 40' 'baby hi-cube' cars and IIRC broke two of the stirrup steps and lost another one just separating the chassis from the body. I had to buy some new ones (Detail Associates I think), not expensive but another cost to an already fairly expensive car.