You're getting a new, built to order class A and they promised it in 6 weeks? Does that seem right to you? Obviously not, because you've asked the question. I would certainly get a second quote. If I remember correctly, you'll be in hotels in the US until you get in your coach and start your adventure, yes? Think about the cost of an extra month in a hotel waiting for delivery.
Also, with a new coach, you'll need to stick around the dealer's area for a while to get things fixed that the factory leaves for the dealer to do. Think about trying to schedule that into Camping World in April and May when everyone else is pulling out their campers for the season.
IMHO, you'll be doing well if you get on the road by the summer.