Good luck, and have fun! Running is a great hobby, especially if you have access to some trails instead of just roads (much more boring). These adventure races are a great way to keep things fun and interesting, especially if you can get a team together.
As a fellow "old guy" (well, sort of...41), if you're starting out just go easy at first and work your way up in terms of distance / speed. I'm just getting over a 14 month bout of plantar faciitis which has had me side lined.
If you're new, I recommend going to a specialty running store and have someone who knows what they are doing watch your gait. Correctly fitted shoes will prevent a lot of injuries. A lot of stores also provide running clinics / coaching. It's worth going, you'd be amazed at how much form makes a difference too.