same here @ 43.Started doing EFTA races this spring. I have to say that w/o taking too much risk you can get yourself up in top 30% of racers by just plain conditioning and getting ready for the season. I've started training using this URL http://home.hia.no/~stephens/mtbplan.htm - simply adjust the amount of hours that you're putting in a year and the spreasheet should work. If you want to win, however, you'll have to take certain risks. I'm losing most of time on dowhills, anything above 20 mph on a dirt road kicks in my safety and I slow down. Technical sections can be learned but you have to do lots of them and it will come after doing year or so racing. I spend ~ 200 hours/year training (if this can be called such) but for novice vet is enough. Equipment matters also, you won't make it on trek 820 or such and I wish I have gotten right away FS bike. Huge difference, but it's up to you to try the sport and if you like it then invest in a nice bike.
Hope this helps.