Some of the best drivers in the country run in the stock classes. Because of R-Compoud legality in the Stock class, you can often go faster than the STS/STX guys anyway.
And I agree, you really don't know what you car does/should do/you would like it to do, until you take it out there and push it to the limit. And even then, most of the time you could get what you were looking for with better driving anyway. I see a lot of people spending $$$ on equipment that's just a crutch for their bad driving skills.
Don't waste another minute waiting on parts, or anything else. Just get out there and start racing! You will suck at first, and you will be slower than many other cars, but the only thing you will regret is not starting earlier...