Wow, you sound just like me! After the end of my highschool and club seasons, I really wanted to pole vault, or maybe run something on the highschool track team. It's a no cut team, so I gave it a try, and only went to gymnastics on saturdays.
A couple weeks or so ago, I got back to the gym, full time. Here are some things that could be helpful...
1. Drink lots of water, and give yourself some time. You will probably get a little light headed tumbling, and things that came easy will be at first a lot harder. Don't be hard on yourself. Your coaches will probably be understanding, and if you feel too worn out, sit down for a minute. You'll feel better quick, but your body isn't used to the intensity of gymnastics. (Also, you don't want to push too hard too fast, you'll be at risk for a stress fracture-- no fun!)
2. Arm strength. Your legs are most likely in pretty good shape, because you did track! Bars, at least for me was the hardest event to get back into. To get your hands stronger, you can squeeze stress balls, or anything squishy. Trust me, your hands will be tired after going on bars!
3. Finally, don't be afraid of the basics! It will be hard at first, but you can spend awhile getting re-acquainted with gymnastics. In a few weeks, you won't be able to tell that you left! Goodluck, the first week back can be tough with the sore-ness.
She was just starting up again!
That's all I got for ya... well, good luck, and have fun! 
And I am going to be so sore!! Ahh but I will get over it..
