It may help if you post some pics of the bad areas, Hopper. If its just small spots and the rest is good, you may just use some patch panels.
And if you can MIG, then you can do it. Just do like FMX said and stitch it in places so as not to overheat it. Its time-consuming, but beats paying a shop to do it lol. And whatever ya do, dont cut the whole floor out at once unless you have it braced to prevent flexing.