Congratulations. IMHO every Jayco should have a sticker inside a cabinet door with the JOF URL. This is a great place to learn all the things your dealer did not mention.
And, as CarlB noted, the tankless water heater can be a bit challenging at first. After a learning curve, it works fine for us. Basically, for cooler water, open the hot water knob more. For warmer water, close it down some. BUT, do not close it down too far. If you slow it to a trickle, the small amount of water being passed through the heater will get too hot and a safety switch cuts off the heater. The rest of your shower will be quite chilly, as I am very aware. To reset this safety switch requires going outside and locating the tiny, unmarked, secret button in the water heater compartment which is not mentioned in the Girard manual.
But you're going to love that Greyhawk! All RVs have their quirks.