I bought the coach used and it only had 11,000 mi. Had the brake recall done as soon as I got it home. Not knowing how well the original owner took care of maintenance, I had the transmission serviced at the same time. I put all new Michelin Tires on it, and they are now 6 years old, and look brand new. The coach is stored inside. We have only put 25,000 mi. on it in 6 years, but I am retiring at the end of the month. This is what we have been waiting for. MAF sensor was replaced in SD 3 years ago. I have never touched the plugs and wires, but I will do that before the trip. Even though the tires look good, I think I may put new fronts on, and take the existing fronts as spares. I will be pulling my 2015 Colorado on the trip.
To answer the tire pressure question, I run 90# in the fronts and 95# in the rears. This is based on the weight on each axle when we are fully loaded.