ASV 5420

Greetings, I recently purchased an ASV 5420 (John Deere 115 hp) with the intent to give my son (17 year old) hands on (mechanic) work experience. He is in trade school and has interest in diesel/heavy equipment service. He has been working on a Ford 1720 and a 555E. That said, we appear to have acquired a ASV 5420 real life learning lab. We paid $4,750 - delivered. The machine was reportedly on a farm and does not appear to have been cleaned often so this is step 1. It does not look like the machine has been used in some time. We have removed enough dirt to start a garden. Power wash is next. We pulled off the floor board today and to my surprise was a pristine hydraulic fluid sump. I noted one hose in need of replacement but otherwise I was a bit taken back as to how clean it was - it looked brand new. The machine does not start. This appears to be a combination of poor battery, a starter needing to be rebuilt and an injector pump needing to be rebuilt. All of these will give my son some good practical experience...especially the injector pump (engine TDC pinning, etc.). If it does not start after these replacements the machine may be parted out. As best we can tell the machine appears to have 2900 hours. Is this high? Maintenance and use history being a major factor of longevity, how long might a Powertech John Deere 5.4L last. If anyone has any experience with this machine your insights would be appreciated. Any idea where we could get an operations and/or maintenance manual.