Roach, good on ya. I also took up road racing at the tender age of 39 (CCS) and while it is undoubtedly one of the riskier endeavors in life it was one of the most intense, awesome and all consuming things I did in my life too. I only raced two years, so take this with a grain of salt, but here's what I'd do if I were doing it over:
Race a "sportsman" class where engine mods are limited. Stay out of an engine arms race.
Optimize your chassis/wheels around the best tires available and legal for your class
Spend your money on suspension, definitely get it sprung correctly for you of course.
Vanson leathers that fit. The end.
Make friends. Go meet all your class competitors, check in on them after they crash, swap parts and help. The camaraderie among racers is pretty awesome.
GET FIT. This is the biggest variable, all other thing being equal. Being fast and smooth and safe takes great core and leg strength.
I hope you will take us along on your journey, I'd love to re experience this vicariously through you. Have a ball