the most important thing will be to have the wheels gone over by someone who really knows their wheels.
What do you mean have their wheels gone over? It's a new bike. You mean to look for factory defects?
I would strongly suggest also going with the widest tire you can (ish) as the lower pressures will make life a lot easier on the wheelset.
It comes with a wide tire by default, but I was thinking I'd switch it to thinner road tires and put the thicker ones on it when I'm going off-road. Bad idea?