First and foremost, best of luck to you and the ones you provide for, on your new journey. I hope that you find that the grass indeed greener on the other side. There are a few hurdles involved with such an endeavor. A new hire, no matter how long in the industry, must prove himself all over again to a certain degree. You have to get a new bay organized to your liking so that efficiency can be maintained, you have to due an inventory of all the special tools and you pray they have everything or more. You have to get in good with the parts department [most important of all] and there again you hope they know what they are doing.
I would say that one of my keys to a successful move has been to stay the course and not waiver from my work ethic involving automotive repair operations. In other words I have a system that works, I have stuck with it, and management (new or existing) has never been able to change me.
Take it easy the first few weeks and triple check everything you do. This will prevent stupid mistakes that if happened at a place where you are at the top of heap, would be swept under the rug or never even noticed, however will be heavily scrutinized as a new hire.
Lastly, I gotta say that your exiting dealer has got to be up in arms. That is going to be a huge void for them to fill and last I heard they were booked out for months.