The BIG Switch! (advice requested)

As I wrote in the previous post, Pippi is on the mend, and we will soon (relative term isn't it?) be riding once again. The date for the mount up is set for December 29th, unless there is a downgrade of her condition by then. She might even be fit to ride now, we are lunging, but I want to wait longer than necessary as I am afflicted with a condition called Worry-Wartism.

Anyway, a momentous decision has been made in lieu of the type of injury she sustained. We are switching disciplines and will from now on be, Drumroll please, doing Dressage.

DRESSAGE!!!

Yeah that's right, Dressage! I have mulled it over for a while now, and I just can not talk myself into the idea of Pippi jumping again. The tendon is always weaker after a bow, and it is just not worth the risk when we could so easily switch. As stated before, I don't really care what we do, as long as we ride and learns and grow and have fun. I was jumping Hunters, because that is what Pippi does, and so if Pippi doesn't, well then I don't either.
The good news is that current BO can give me beginner lessons in Dressage, as she has a working knowledge of it, and can at least get me started. I really cool friend, offered to let me ride her horse to see what a dressage horse feel like, and I will take her up on that for sure. So I can ride my own horse, and have lessons on my own horse, and do it at home? Whats the downside? Not seeing Kara as often!! And that is a biggy for me as I adore her. I have not told her yet, but will this weekend, and I am sure she will understand. I would love to take Dressage lessons from her, but no truck to get Pippi there and I would rather take lessons on my own horse.
The plan is to start lessons as soon as Pippi and I are in fighting shape, so late January perhaps....

Meanwhile, with my scarce knowledge of Dressage, what advice do you have?
Start with what?
Work on what first?
What makes you love Dressage?

Thanks