If you get underneath the car, you don't need to pull back the carpets, just start touching the floor to see if it is solid. Though it is usually a good idea as often the foam gets soaked in water and starts rusting the floor from the inside out, this was happening on mine.I need to get under the carpet and see what my floors look like.
The body on my car has rough spots, but looking under it I think the floor may be ok.
Yes, this is correct. Only needed if you are getting into the rockers / frame connecting rails. Sheet metal repair needs no bracing what so ever, even a pretty significant amount of it, just cut out and replace. Remember to coat both sides with your preferred rust treatment and top coat with tar / undercoat material.Bracing was required on this project because we were cutting out a large portion of the rockers. If you are doing a 5sq inch patch around the drain plugs, I bet it isn't necessary to brace.