1997 Chevy Truck Broken Pushrod

Engine Mechanical problem
1997 Chevy Truck V8 Four Wheel Drive Automatic 114k miles

I have a very clean 1997 Chev C 3500 I Ton Dually 4x4 which I bought from my sister 4 years ago. I've never had any trouble with the car until this week. My wife and I we're driving the Chev from Los Angeles to Reno, NV, by way of Death Valley. The 2nd day of our trip the truck broke down near Tonopah, NV. Had a mechanic diagnose the problem as a broken pushrod in #2 cylinder. He couldn't do the work, so had the truck towed 112 miles to Bishop, CA. The car should be ready by next Wednesday. The estimate is $1000 to install a new pushrod and rocker arm. Is that a good estimate?? Also, the mechanic in Tonopah said that the tappet would need replacing and that I actually should replace ALL of the tappets while they were doing the repair. The service manager in Bishop says there is no need to replace any tappets at all.
Many thanks for your help.