You have to be careful trying to just piece in patchwork. Everything inside was installed after the floor was built, so the floor sheeting is in one piece across the entire width of the unit. This is needed for strength. To repair it properly, all the stuff in the way needs to come out first.
In answer to your question, yes, this can be done as a DIY. It is essential to have a closed place to do this, a shop, barn or something similar.
To get an idea of what is involved taking a trailer apart, have a look at my
Rebuild Project.
There are different construction methods amongst the various brands. Check to see what yours is.
Mine was 2X2 wood stud framing, 2X3 floor joists. The aluminum siding was stapled directly to the studs, no sheeting because that adds a lot of weight. The interior was 1/8" wood paneling.