Box removal and installation is a simple process, provided you have the proper torx bit to remove the box bolts. That said, the clips that hold the "nuts" on the bottom side are likely going to break free and spin. My best piece of advice here is to start a daily regiment of WD40 right now from both the top and bottom side of the box bolts. And keep doing it every day, at least once a day for a couple weeks minimum. Do it every single day until the time comes that you have to try to crack them loose. If they break free and spin, you are likely looking at grinding the top of the bolt off, and have to lift it up and over that much higher. Then you will need to figure out how to get the spinning bolt out of the nut/clip that is left. Also, watch out for a ground strap attached from the frame to the bottom of the box. Removing the rear bumper makes life easier too, especially when installing the new box.
Fenders are bolt on, but they are still quite involved. Easily do-able and as straight forward as life gets. You will have to remove the windsheild cowl, and headlight mounting panel though, and if memory serves me correctly, I think you need to pull the plastic fender liner.
For door assemblies, alot depends on whether the door you are getting has the same options as the current "old" door. If it does, you just need to pull the door panel off, and t make life easier, remove the door glass (lightens the load too), unplug all the electrical points, and feed them out the door through the plug hole. Then remove the door opening catch, and undo the 4 hinge to door bolts, leaving TOP ONE FOR LAST.Have a strong friend hold the weight of the door for you when undoing the last top bolt. Reverse the process, to install. to make life easier, pull the fender first, then take all the wiring ect out of the door, and remove the door catch. Then close the door and pull all the bolts. Then open the door, and catch it before it hits the floor.
Same process for rear door as front door. Door skins are not a "weekend warrior" project. They take skill, and some background knowledge on hammering and dollying. If you are not a bodyman, steer clear of this project.
For your re-assembly process, install the rear door first, and make sure it is aligned properly to the opening before moving to the front door, and align it properly before moving to the fender.
Door alignment is something you are going to get a crash course on. When doing it, remember these simple steps. First get the proper height, so the body lines are correct. If you undo the bolts on the bottom hinge, and pull the door out at that point, the diagonal corner of the door is going to do the exact opposite, like a teeter totter. It is very important that you get the rear door aligned first before proceeding to the front door.