Getting towards 600k , time for a rebuild soon?
The transmission has been replaced in 2013. There is nothing wrong with Voith transmissions; they are popular choices in Gillig buses. It is just harder to find someone who knows how to work on them since they do not have the overall market share (for trucks and buses) that Allison has in this country.
The reason for transmission replacements in transit buses is the wear on the lower gear clutches in that application. If you use the bus over the road, the transmission is going to last substantially longer since it has to go through much less shift cycles. (BTW, I was looking at three Gillig transit buses where the Allison B400R transmissions were replaced after about 250k miles. Does that make Allison a bad brand? No, it just confirms that never ending stop-and-go operation is a bear for any transmission)
The engine of the bus you linked is a Cummins 8.9L ISL, a stroked derivative of the 8.3L ISC. If the engine is indeed the first one, it's going to be tired but replacement ISLs can be found from wrecked class A RVs. That may sound like a scary proposition but keep in mind that this swap will not only get you a fresher engine but will also get you from the typical 280 hp configuration for transit buses to the 380-400 hp configuration for RVs. I would drive the bus around with its original engine while converting it and then install a more powerful low-mile ISL when coming across a good deal. Since you are not lugging 50+ people around while constantly burying the gas pedal, the transmission will handle the additional horsepower. Also, the ISLs variants installed in buses and RVs are electronically limited to the same maximum torque in order to protect the transmission.
The bus in the linked photos is a Phantom, also known as "high floor" transit. You will have 78" of stand up height in the center throughout the interior length of the bus. Above the windows are angled ducts on either side of the bus that you need to leave in place. They reduce the ceiling height near the windows and you have to cutout the partition walls accordingly. The bottom panels of the windows will open (originally as emergency exits) and swing out around a top hinge. If you prop them open with a rod, you will have great ventilation being parked. There is space under the floor to install water tanks and other stuff but it is not as much space and not as easy of a job as it would be on a motor coach having baggage compartments. Some people have closed the rear door and used the former stair well space for a sunken shower. Sinking the shower pan into the stairwell makes up for the lost height from the ducts running along the sides of the bus.
Gillig also makes low floor transit buses that have a huge amount of head space from about a foot forward of the rear wheels all the way to the windshield. However there is no (zero!) space under the bus to install anything in that section. You would have to install a raised floor under which the water tanks and other utilities are located. If you raise the floor, you may also be able to use the ridiculously tall front wheel wells for seating. The rear section of the Gillig low floor buses has a higher floor from the factory and there is not enough height for anyone North of 6'. That basically means that tall people can use the rear portion only for bed and storage and have to cram all the rest in the front section, which is not a problem on a 40 footer. On a 35' chassis this is going to be a challenge though. (Reason for rambling about the low floor model is that the
VIN decoder lists the bus as low floor, whereas the photos show a high floor Phantom. Either way, you will be fine if the bus is 40')
Since I am looking for a 35' transit bus, my choice is the high floor Phantom for the reasons listed above. I am not going to have a "cathedral" ceiling anywhere, but at least a solid 78" from the windshield to the rear bench.
If the price is right and the bus suits your needs, go for it. Nothing is perfect and exempt from the need for repairs, replacements, or upgrades. Personally, I would bid on that bus if it were not a 40 footer and located on the wrong coast for me.
Hope that's enough of an opinion...