Hi, I would never wish to discourage anyone from digging into a project like this and like wovenweb says no one is judging you or your abilities. If this is your first attempt at welded panel replacement then I would recommend that you start with an easier project like maybe the bottoms of your fenders or inner fenders under your battery.
The full trunk floor will include the shock mount, you may have to save a reinforcement off of the old one to install on the new panel. The trunk floor replacement usually requires tailpanel removal and often is done in conjunction with quarter panel replacement as well as both trunk dropoff panels. With replacing a frame rail at the same time you may be able to get the panel in from underneath. One of the keys to success on this project will be how you support the rest of the body during this time when you will have very little strength in the back end. I would remove the interior, 1/4 glass, back glass and anything else with any weight in the back of the car and either remove or protect anything that may be damaged by sparks or welding. Large pieces of cardboard work well for this. The body should be supported under the rocker panels and under the front subframe so that the remaining weight in the front of the car is neither hanging down or lifting in the firewall area. Remember its a unibody and uses the combination of all of its pieces to give it its strength. A brace across the door opening from the top of the quarter to the lower door hinge area is also a good idea.
Although this is a big project for a newbie, if you have some mechanical skills and some welding skills and lots of time you should be ok. Please do not try to do this with structural adhesive. save those products for minor non structural patchwork. good luck . Neill