300 te wire question

[Eliot]

In my 1989 300te, the wire/ cable that enters the external fuse for the fan (driver's side, just outside the fuse box- small black box that has one metal strip) has degraded about 1/2" before the terminal. I need to cut that wire and splice in new stuff.
What gauge would that be? How would you all do a splice? This is only for, maybe 2" of new wire...then it has a terminal (hoop) that connects to the external fuse holder.