Before you accept delivery, check the date code on the tires. With it being a 2013, if the tires on it show much more than 2-3 years old, I would tell the dealer they need to be replaced. What you're looking for is the last four digits after the DOT stamp. There's a lot of opinions out there, but if they're more than 7 years old, I would definitely get new tires before a long trip. You're probably talking about $3,500 or so for a full set with stems, etc. As for the water heater, if you have a tank type, you most likely won't have any issues. It's the demand (tankless) type that can be a pain but mostly you just need to understand how they work. There are a lot of different things that can cause them to malfunction but they're all fairly simple to troubleshoot and repair. Have fun regardless - all you can do is go with the flow. All will eventually be fine!
2015 Legacy SR340 360RB
2014 Jeep Wrangler Unlimited Toad
Gigi, Poppy and Sadie Lady...On the road, but not full time!