NO YOU DONT! Its very simple and have done this hundreds of times on customers cars and even postal vehicles.
1. Take the driveshaft off.
2. take a small chisel and lightly hammer a small line on the top of the nut.
3. take same chisel and put a line on the end of the pinion shaft that lines up with
the line on the nut.
4. take an air gun with socket and slowely remove the nut counting the revolutions
for reference i put a "white out" line down the socket.
5. it'll get very easy to turn towards the end so just turn by hand so you don't miss
revolutions.
6. remove yoke and pound off old seal using same chisel, catching the outer lip of the
seal and forcing out of housing.
7. clean area with rag and install new seal.
8. reinstall yoke, install nut and turn exactly the same amount back to the lines you
originally marked.
I even put it a 1/16th to 1/8th tighter. it helps to reseat the bearings. I find the crush sleeve will give a little over time so putting it that extra little bit is just enough to get back to specs. It's a proven method.