I would say no to updating the axles unless you are having a problem. You can upgrade the tires and wheels w/o the axles as long as you keep you weight at or under the GVWR. The best thing to do is to weigh the rig as you normally tow it so you will know how close you are. Lippert/Heartland upgraded my axles to 8000 lb when I was in Elkhart. I had an axle problem, and they weren't sure what caused it. I wasn't that heavy, but I was close to 16K. I can tell it is stiffer but would not have gone to 8K out of my pocket. Personally, I would change the tires before the trip. Kind of like russian roulette with the Chinese tires. Many never have a problem, but many, like me, have. As for price, check local dealers and shop price. You will find quite a variance. I found a good price online, and a small tire dealer that would mount and balance. I know Jim B and a few others got an excellent price from Sears.