Power Steering Box - 420 SEL

[Hans47]

Howdy. My '88 420 SEL is bleeding power steering fluid and I have been told that it should be fixed before the ps gear box bursts. Presently, the car steers like a dream although it’s messing up my garage floor. My technician has given me two options. Rebuild it at $760 or replace with a new one at $1,428. This work estimate excludes the $256 cost to replace the ps hose to the cooler. I'm struggling with a conversation that I had with the shop owner. For the rebuild, he claims it could cost more if they encounter unforeseen problems. My opinion is that since his technician is a MB expert, he should know beforehand exactly what the issues are and build them into the fix cost estimate. Am I being unreasonable? The shop owner also mentioned a third option which would be buying a factory rebuilt ps gear box in the $800 range which would reduce the rebuild risk. Although it sounds like he couldn't find one so if anyone out there knows where I could find one it would be greatly appreciated. Thank you.