Thank you all for your input! Many different opinions out there! We are going to a CAT scale tomorrow to weigh the truck as it would be loaded for a camping trip, and then after we pick up the fifth wheel next week, we'll do the same with that. Then we'll see where we go from there. I've been on a few other forums regarding switching out the 3.73 axles for 4.10, and it seems as if most people don't think that will make much difference. Most posters seemed to think a jump up to the next highest axle ratio would be more helpful.
Our plan is to take the fifth wheel up into northern Michigan for a long weekend, just to see how it handles. After that, we will be doing quite a bit of traveling in it (Florida in the winter, and road trips to various national parks in the summer), and of course we will have to drive in mountainous areas. Since we are retired, we have no time limit on when and where we go, and can definitely take our time getting there!
Thanks again!