Truck Repair: b or c series engine, crankcase breather, dodge diesel

Question
i have an 1989 bluebird school bus that i converted to a motorhome. my son used the buse last weekend with his buddies, he is 22 years old, should'nt have to say any more.
we currently own 3 dodge trucks with the cummins engine 04,99, and 98 that my son owns. we picked this buse based on our good experiance with these other trucks.the above buse has 125,000 orginal miles, we have the records from the school district.now the story: my son was traveling in southern utah and noticed that the bus was showing hot on the temp. gauge. he pulled over, let cool down then added 1 gallon water, traveled another 100 miles to camping spot with no problems. after 200 miles on return trip the engine showed no oil pressure, he pulled over found oil covering bottom off the bus with oil coming out off crankcase breather tube. he add 2 quarts of oil to get to closest town, then add 1 gallon oil, engine runs rough at idle but smoothes out at higher rpm, went 45 miles then add more oil. i called our local cummins dealer with ser. # but i had the wrong one will look tomarrow in the right location, don't know yet if i have c or b series engine. if need repairs question aprox. how much ? can the repairs be done with engine still in bus ?
if you have any ideas please respond back'
thanks

Answer
I afraid to say that he probably scored a piston.Usually #1 cyl when they run hot.Oil lose from blow-by tube(too much pressure in the crankcase from scored piston).You can check for which one it is by breaking loose the fuel injector lines at injector one at a time.But be CAREFUL! High pressure fuel can cause harm to you.All you have to do is while it is running,loosen the fuel line nut(just until you hear engine sound change)and do everyone until you find which one it is.If it is a C series(8.3L)You can rebuild it in the chasis.Im pretty sure you have a B series(5.9).It will look just like the Dodge diesel engine,single valve covers for each cyl.A 6C has one long rocker cover.You might want to check on price of an engine,short block & long block.You will have to remove engine to get block bored out if it is a B series.But I hope you dont have that extensive of damage.