This is an impossible question to answer. There are about 50+
wires that run through the firewall. You wrote "I had a short in the
wiring and one wire burned all the way to the firewall. The
connection is rubber and looks like it might unplug but I am not
sure. I need to replace just that one wire. I need details on how that
wire is run into that rubber connection."
That description describes almost all of the wires in the entire
vehicle. But I will attempt to help anyway.
1) you have to see WHY the wire chard and the fuse didn't blow first.
Fuses are put in to exactly avoid those issues. The fuse obviously
over rated for that wire, or that wire is underrated for that fuse. But
what I do is after finding out why that happened is run my own new
wire.