Ah, we are narrowing it down.

The front output seal is not too difficult to change, but it will take either a big breaker bar to remove the nut or an impact gun. Putting it back will also require it to be torqued to some pretty hefty number.

It is smart to also replace the nut. It is a staked nut and reuse is not advisable as it will screw up the threads.

Good Luck,
Michael