You're bound to run into some issues, that's just the nature of the beast. Hopefully, you won't have any quality issues. If you find something wrong that should be covered under warranty, get it fixed immediately. Assuming that you haven't picked up your Navion yet, if there are any issues with it, do not sign the purchase agreement until they're fixed! Perhaps your dealer is great, but there are myriad stories of dealers promising to fix issues "next week", which in many cases effectively means "never". Once they have your money, they have no incentive to make any repairs quickly. Your signature is your only leverage.
Getting an independent, third-party inspection before purchase - even on new RVs - is a very good idea, since you won't know what to look for.
Once you have your new rig, I suggest doing some short "shakedown" trips of 1-3 days to learn about the systems, and how you want to use your Navion. It's an ongoing process and you'll likely make many adjustments over time. Read your Winnebago owner's manual thoroughly and at least skim through the Mercedes chassis manual. Make sure you have basic mechanical and electrical tools and supplies. Test every system thoroughly; water pump/faucets/showers, heat, A/C, shore power, generator, solar, lighting, slide-out, awning, window shades, locks, appliances, and whatever else you can think of. Make sure it's all working before you take any long trips. It's much easier to deal with issues at home than on the road.
If you don't have a Tire Pressure Monitoring System (TPMS), I strongly suggest getting one. Otherwise, you're effectively "driving blind" when it comes to tire pressure, which is critical to safety in our heavily-laden vehicles.
Dump your gray and black tanks at least once before you take any extended trips, so you're not trying to figure it out while in line at a campground. Fill your water tank at least partially so you know how.
Spend some time just driving around and parking to get used to the size of your Navion. Backing up into spaces can be a challenge if you're not used to it. Your rear view camera should display parking assist lines, but you may need to adjust them.
Once you're at least somewhat comfortable, go out and have lots of great adventures!
FWIW, if we were ever to replace our current rig, the 24T would be our floorplan of choice.