Not many shops around here want to touch it because its a diesel. But a few that did, quoted between $3,900 and $4,100 for a rebuild on my current engine. I can replace with a used for way less then that.
I did that on another unit about 3 years ago. A low hour, used engine from eBay cost me $900 shipped to my loading dock.
Walker MD-GHS (7,100+ hrs!!)
2x Walker MD-SD
Sterling Acterra dump
John Deere 244J articulated wheel loader
Deere 4320 tractor, Cab w/ heat and A/C
Gator 6x4 diesel
01, 06, '13 F-350