unless there is a world of difference between the 00' and 03' TJ, its not that bad, but a bit involving.
Starting from your axle on stands and tires/brakes off
1. pop rear cover and drain.
2. Rotate carrier to gain access to pin
3. Remove pin (small retaining bolt be careful)
4. push each shaft in a bit to allow the C-clip to come undone, and then remove axle shaft.
5. Remove old seal and replace (Might as well replace the bearing, or at least have one on hand just in case)
6. reverse process to install axle. When I push the axle in to hold the C-clip I push the axle stub back on the clip from the inside of the carrier to hold it. Install pin, add a dab of loctite blue to the retaining bolt, and reseal/refill the diff.
Snags you may come across are lockers or limited slips. you may need some tools or difference procedures to gain access to the pin to remove it and allow the shafts to come in and C-clips to be removed.