the start of the Dart clean up

A trunk floor isn't a deal breaker by any stretch. How's the important stuff? Frame rails, cross members, ect. What's your experience level?
the floors are shot as well as all frame rails they are there but rotted badly I am hopeing to take measurements and replace them one at a time from the front to the back I have never done this type of work before so I am going to move slowly I have all the shop equipment needed to do the work. the firewall and toe kicks are solid as well as under the rear seat. the rockers are also very solid with no visable rot when you open the doors or feel under the rockers. as shown in the pictures the center of the trunk floors is rotted but the rear panel and side panels are fine.