Marty,
I'm right there in the boat with you, 50-54 YO group, first year back, many recurring injuries early on (Hamstrings, Achilles), and 10' in practice. Before I picked up a pole last Dec, I started getting in shape the prior summer. I wasn't truly a couch potato, but 30+ years of nothing but distance running (jogging really) - I knew I wasn't strong enough or ready to start vaulting.
I recommend P90X, you don't need the diet plan if you eat fairly healthy. I found that I was very hungry the first 60-days. Add extra protein to your diet. I started by picking up a used set of P90X DVD's from eBay, and bought some dumbbells on craigslist. I was horrible at first, but after 3-months, I had noticeable and meaningful results. Enough to inspire me to keep going with the program. After 90-days, without dieting or foregoing beer, I dropped 10lbs and was a lot stronger. I added sprint training this past spring. After 6-months of P90X, I've dropped nearly 20 lbs and am down to my college weight of nearly 30 yrs ago (when I last felt that I was in-shape). The ab workout is fantastic, the Plyo workout is killer, and don't skip the yoga or stretching workouts. It is total body strength training with very little equipment required (dumbbells and a pull-up bar is all you need – and something to play the DVDs).
I plan to do P90X again this fall, and add Olympic lifts. Another masters vaulter I met recommended Insanity. I haven't tried it, but if I can get a cheap copy, I will give it a try. My suggestion for P90X is to start slow, take frequent/longer breaks at first, don't try to keep up with the guys/gals on the DVD at first. At our age, it comes slower, and we don't add muscle as quickly. If you haven't heard much about it, check out this video that convinced me to give it a try.
http://www.youtube.com/watch?v=825HotL_cdMIt really does work - you get stronger, you lose weight. The downside is you need to dedicate about 60-90 mins a day. I didn't start out doing it every day, I eased into it by trying every workout and took a day or two off between workouts. After one trip around the package, I stepped up to 5-days a week. At first, I dreaded the workouts, but after a few months I eventually got over the hump and loved it. I'm looking forward to starting up again, but know it will be a tough but familiar road. Hopefully, I'll get to the “love it” phase quicker this time.