Congrats on your new addition and I am going to anxiously await pictures.
I have trained 2 mustangs and the only suggestion I can offer is that if you've never gentled a horse before, it would be in the best interest of both you and your mare to get help from a reputable trainer. Mustangs tend to have a heightened fight/flight reflex and if you push even a bit too hard, they can and will turn on you. That's why I ended up with my first one, because he had terrorized the people who adopted him.
However, after they are gentled and begin to have a bit of trust in you, they are extremely loyal. Both of mine made really nice horses. The first one (the one who was really aggressive) is my heart horse and will be with me until the day that he dies. The other, I gave to the daughter of a good friend and then spend hours every day riding trails, towns, and just having fun.