Wow! Your tentative plans sound exciting! I have a few recommendations for getting yourself in shape. My first is, and I can’t emphasize this enough, STRECH! You need to do that before AND after your exercise regime. When you start building up strength it can be a bit traumatic for your joins, so if you don’t want to get injured you need to stretch a lot. My second recommendation is to start out small but be persistent. Once you get started the key to getting and staying in shape is to be VIGILANT. You need to do certain exercises EVERY day. Well, 6 days a week. It is good to rest your body too. So pick one day a week to be your day of rest, but really discipline yourself to a regime of pushups and sit-ups (or crunches) every day. Start with 10. Then the next week, bump it up to 15. Keep that up and I promise that after about two or three weeks you will already begin to notice an improvement.
The pack test is many a cardiovascular/endurance test. You can start by simply. Go and see if you can do a mile in 15 minutes as a brisk walk and that will give you a sense for how far you have to go. My recommendation is a low impact activity like swimming. Swimming laps is great for getting you in shape. If you are near a city you can sign yourself up for an Ashtanga or Bikramâ€™s yoga class. Those two types of yoga are very physically strenuous. (But be sure to find a teacher you like and who you are comfortable with.) Other activities, like swing dancing, can be a great source of cardio vascular activity. There are a lot of options. (I, personally, am not a runner. I hate running. Running is not the only way, but if you like it then go for it.) You need to get that heart rate up about 5 times a week if you can manage it. That is the key factor. Once you are in shape enough to make it three miles in 45 minutes, then try adding some weight. Maybe 15 lbs and see how that goes. From there you can work up to 45 lbs no problem! And remember to eat right. Sweets and treats are fine as long as they are balance out with what your body really needs.