It appears to be in excellent condition for the most part. The motor is
a six cylinder 404 cu in turbocharged JD diesel design and this one is
apparently a recent replacement. It just purrs. And yes the exhaust
is remarkably clear once the engine warms up. Esp for any diesel I ever saw.
I bet this one could pass a emissions test, no really. The hydraulics seem
very strong and the few minor seeps seem to have simple remedies (so far--knock
wood!). 
I paid a JDdealership $90/hr for 4 hrs for their mechanic to go completely over it before I bought it. After it got here I was lucky enough to have another 4 hours by a local experienced mechanic-operator team, who gave me a lot of great tips on operation and maintenance. All these experts were very impressed and said things like "a real decent machine" and "real solid". That isn't to say it won't require repairs and maintenance, even new ones need that. But hopefully I will be able to baby it along by maintaining it carefully, using it easy, and it will turn out to be less expensive than hiring a machine plus operator in the long run.