You will want to bring some basic tools. Open end wrenches, socket set, adjustable wrench, screw drivers ect. It would be a good idea to bring a grease gun and grease the driveline and steering/suspension components. I would check all the fluid levels before hitting the road including engine oil, coolant, power steering, transmission, differential and brake fluid if equipped with hydraulic brakes. If anything is really low try to locate the leak and repair it before you head down the road. Bring a tire pressure gauge and inflate the tires to recommended pressure. Bring a new set of fuel filters along. If the bus has been sitting it could have grown alge in the tank which could plug the filters. Look up a "pre trip inspection checklist" to give you an idea of everything that should be inspected before driving a vehicle.