Replace a Front Frame Rail - How Much Trouble?

Thanks to everyone for all the input, it's greatly appreciated. All the pictures are very helpful too.

67Dart440GT , Thanks for the tips on the rear frame rails. I'm hoping I don't have to do that but if I do, I can see what's involved. I also hadn't seen a body cart like you use and looked that up. Now I'm wondering if I should try to get one like it, I do have another car to do, non-Mopar, but it'll need tons of work too.