An access hatch would be the best bet, but if that intimidates you, then you could try this: Get the stripped blind nut out. If it's epoxied in, then hold a soldering iron on it for a few minutes, and it will fall out! careful, though, because if it falls out onto some covering inside of the fuel compartment, then it will burn a hole through it at this point. If it falls out onto wood, then you will be fine. Once it falls out, get it out with some needle nose plyers. Now, to re-install a new one up in a hard to reach place, go to the hardware store and get yourself one of those telescoping magnets used to pick up tools and bolts and such dropped into small places. One can be had for about a buck or two. They look like an antenna on a transmitter, but they have a magnet in one end. Put the new blind nut on the magnet, and carefully place it up into the firewall from behind. I've done this numerous times.
Now, for the hole. You could go through the trouble of redoing the wood, or you could just get some covering of the same color and iron over it. You'll have to look very hard to see it, and once in the air it will be invisible!