+986 to what Tom says above.
I've driven Porsches for over 25 years and have wanted to track them almost as long. I got the Spec Boxster bug a while back, emailed and talked back/forth w/ Tom, Brad and a few others and formulated a plan very similar to what Tom's path (above) was/is.
I started DE and AutoX events this past spring. I started w/ my Boxster S, but like Tom said, came to realize I need to be concentrating on a lower HP, 5-speed as a training car. I switched to my base MY 2000 Boxster (since that's the Boxster in my fleet that I didn't mind sacrificing) as my DE and AutoX car. I've since purchased a '99 that will be my spec car and will soon begin the process of building it as a spec racer.
It IS extremely time/expense consuming to get on the track with an instructor, watch and learn from every event you can, and do the research, reading and studying on how to put a good car together and how to be an effective driver, At times it is almost an obsession.
My professional background is as an Air Force aviator, and I spent many years studying, learning and instructing. Being good at something, becoming better, and understanding the workings and limitations of both yourself and the machine takes time and patience.
Tom said this about racing, and it applies almost word for word with flying military aircraft "The reality is that racing is life. Its every emotion, every challenge, every battle, every joy, every burden, every fear, and every blessing. Its raw, its passionate, its painful, its humbling, its freeing, its dizzying, and its ecstasy.
Its all of your years of living wrapped into 1 minute and 33 seconds. Its like taking a cup of life, pouring it over your head, and letting it wash through your mind and body."
I've already found these emotions in my scant 6 months of my journey to Spec Boxster racing. I had a lady friend ask me just last night, that why at my age (56), do I still feel like I need to be competing against other men. My answer to her is that I was competing against myself and how close I can come to perfection. Plus it's a lot of fun (and a moment or two of fear)!
Follow the path that Tom has laid out and you'll be well on your way to Spec Boxster racing, and along the way, you'll find a whole other dimension to yourself and your life.
Good luck!
Rick