the 7.3 while it was a good engine has many issues with it and will have some due to age. leaking bellows on the exhaust, might have a bad HPOP injectors could need R&R. Like you I searched for a diesel found a couple but the coachs were not suitable to the wife. So if ya can get a scanguage and take the rig for a good test drive with it installed (obd port) check for codes and anything else it shows.
Actually you need to find someone with knowledge on the 7.3 to look over the eng/trans to help ya decide if its the deal you think it is. My BIL has had several but bought the infamous 6.0 and said he would never go back to the 7.3. Its only advantage performance wise was mileage was better. He made his living as a logger and has worn out a lot of vehicles I can remember his 6.5 and the later PSD's. Another issue with the 7.3 is cab and external engine NOISE so just be aware.
