I am currently redoing a quarter replacement for a customers 68 Camaro. The original replacement was a poor stamping in the jamb area which would not allow the door and front clip to align properly.
I guess I can't say this job is easy at all. Even the replacement panel is quite a poor fit. I'd have to rank this as a "not for newbie" job. If you have a friend that has done body replacement before it would help a great deal. When you place the new quarter up into the new location and it looks too long at the tail panel, won't snug up over the wheel well, and the gap at the door is -6mm at the bottom it will help a great deal to have someone with the "eye" to know how to make it all work.
More than likely you will need to also replace the inners, outers and trunk drop offs as well.
I think you can save a lot of money taking the old parts off, which is not hard at all simply time consuming and somewhat putzy. Prep any areas that may need attention and then take the new parts to the body shop. I think you'll save significant dollars that way.