A single analysis can tell you some things. But what if the oil was recently changed? What if it was used oil that was put back in to hide a big problem?
I would do the oil analysis, just be careful about reading too much into one snapshot.
If you can drive the bus, take it for a 30+ min ride (longer is better, or so I hear
) & put it on the hi-way before you take the sample.
just my $.02 worth,
Enjoy the trip to look at the bus, and remember, there are lots of good ones out there, so don't settle for a basket case.