Welcome to the community.

You'll be happy to own the Xterra, for sure.

Premium fuel is needed for the Xterra, but it only adds a couple of buck per tankfull, so it's not that bad.

If the vehicle is cold when you pick it up, start it up and listen for any ticking sounds, especially from the right side of the engine. X's (and Nissan V6's in general) have a tendency to have a cracked right hand exhaust manifold, common.

When you get back home, have someone (a shop, a dealership, Pep Boys, etc) run the codes from the computer for you. There could be a code stored without the light being on. Get that checked, for insurance. If anything is stored, get it fixed, you'll be happier afterwards.

Don't top off the fuel tank! Fill it until the nozzle clicks off, then pull the nozzle out and put it away. Clicking more fuel into it can (and will) cause the light to come on.

Otherwise, drive it. Play with it. Take it off road (it'll really like that, they get cranky if they don't see dirt once in a while). Even if it's 2wheel drive, some fun in the mud doesn't hurt.

Enjoy it!