If there is a tool to hold the door similar to what the factory used then it would be easy. The problem is the darn thing is heavy and there is no place to support the door as it is placed in the opening.
Imagine you could get a ford factory door clamp on a rolling cart. With the fender removed to wheel the door into position, check the gaps, and install the upper and lower hinge. Next you remove the door clamp, and install and adjust the striker bolt, close the door and you are done!