Read up; hit the back stacks of skoolie.net.
It's got a Caterpillar 3126 engine. People like them or hate them. Experience (not mine) seems to be that they run as well as and last as long as other major brands, but Cat has the parts market locked down and charges like they have the market cornered.
It has an Allison AT 545 transmission. No lockup on the torque convertor. Ok sort of for a 3/4 bus like that, as long as you don't mind lessened mpg, additional heating in the torque convertor shortening the life of your transmission fluid, not being able to tow anything of any size, and slowing down on hills.
Tires look OK. Are you in a position to inspect before purchase? If so, learn to read tire date codes. 6-7 years or less is probably OK; 10 or more isn't. If you can't get to the bus, roll the dice. 6 new tires will run you $1800-2000.