The first piece of advice anyone here will give you is don't try to develop the car and your driving at the same. It can't be done. You need to concentrate on your driving. You need seat time not a highly modified car. Since you already have the struts, springs and sway bar you may as well put them on and run in STS provided you have made any other mods. We really need a detailed list to determine your class.
There is no such thing as the ultimate autocross machine. The allowances for each catagory, Stock, Street Touring, Street Prepared, Street Modified, Prepared and Modified are too numerous to discuss here. You can find them in the online rulebook [url=http://www.scca.com/_FileLibrary/File/2007SoloRules.pdf]here[/url]. Depending on what you have done to it, your car is in H Stock, Street Touring S, D Steet Prepared, or maybe Steet Modified if the mods have been made that are only legal in that class. Okay, I just looked at your other post. Removing the reat seats and the cat puts you into Steet Modified. I would recommend re-installing them, if you still have them, and going to STS. I can't beleive they said no one has ever autocrossed this car. It has won at least one National Championship. Greg Reno ran one until two years ago. Many others have used them.
By the rules, you are responible for declaring the proper class for your car. With the mods you list in the other post, it appears that is Steet Mod.
You really don't need or want a fully modified suspension at this time. As I said, you need to work on you driving skills. Hell, some of the best drivers in autocross can't tell the difference between a well set up car and a badly set up car. A novice certainly can't.
Local sponsors? Good luck but it can be done. Just don't expect to get any cash. Look for discounts and freebies from businesses you do business with. The tire shop, the parts store etc.
Muskegon is in SCCA's Western Michigan Region. Their web site is [url=http://www.wmr-scca.org/]here[/url]. They list R. J.Pruitt has the Solo Manager. The is a link to an email address so you might want to send him an email with questions about their program.
I have never heard of helmet rental. Most clubs have some loaners available. The way to tell if a helmet meets specs is by the Snell Foundation sticker inside the helmet. You will have to move the padding around to see it. For autocross, the legal helmets will have the letters SA or M (motorcycle) and the numbers 1995, 2000 or 2005 on the sticker. Any rating stickers on the outside of the helmet are not official and don't count.
Welcome to the sport, Jay. I hope you enjoy it as much as I do.