I would guess 4 hrs. Many shops won't install owner supplied parts. Those that do won't guarantee that they will work.

I had all kinds of trouble with rear main in Cummins. Had new trans, expensive fluid, new Southbend clutch, OE rear main. Mechanic lubed seal and did not use.installer tool. Main leaked bad. Fortunately, owner stood behind it. I drove 1000 mi on vacation in a truck that left oil puddle at fuel stop.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.