Sounds like you are talking about the transfer case output shaft seal which is at the front of the rear driveshaft! The pinion seal is at the rear of the shaft in the differential or (rear end)!! The transfer case output shaft seal is in the middle of the Jeep, just beneath you when you are driving it. Usually, best thing to do is let a mechanic have a look to be sure of no other damage like the bushing behind the seal, if at transfer case!
as far as the wire that is a pigtail and some wire solder and shrink tube. don't use butt connector it will rust the wire. as far as the seal yes it is a pinion seal if you mean the one at the end of the drive shaft.