Was it throwing up a code saying the hyd sendor was bad?
When you say it has 2030 hours is this visable on the meter but just no longer counting forward? It's not just dim and hard to read, because that is just a lite bulb in the display.
These have a rpm sensor (about 3" long,, 3/4" fine threads, with 2 wires coming out the end of it) threaded into the side of the bell housing (on tailgate side) that "counts" the teeth on the ring gear to monitor engine rpm, I'm not sure if it uses this and a combination of engine oil pressure to tell the hour meter when to record more time.
If you unhook the rpm sensor and conect you multimeter to it, you should get a AC current voltage when the engine is running, if its working.
Most of the other sensors in the system can be bypassed by connecting the 2 sensor wires to each other. I doubt the hyd sensor you are replaceing has anything to do with the hour meter.
Check all your ground wires under the cab and around the boss box, also at the engine. Loosen, clean them and retighten. Also check the ground strap from the cab to the chassis. (near the hinge again)
Also there is a spdt relay (used to be near the hinge to roll the cab back, but on the underside on my 93 753 boss, they may have grouped it with the fuses by 98,) it was what the boss used to shut the engine off in event of a shutdown code. Looks like a 1 inch square plastic cube, black with 5 blade terminals on it and it just plugs into the harness. These go bad around 2000 hours and cause the engine not to start sporadically, Cranks but won't start. Its a $10 part at napa, etc
Let us know how you make out.
Ken