I'm in the same boat, with a 944S2.
Your question is bigger than you think.
First, the answer is YES. $100 is NOTHING in the world of racing knowledge.
Second, the bigger issue is the car, and it's relative competiveness and cost to attain that level.
Right out of the box, the 944 handles well, and is a good all around car. But in the top levels of ITS, that's not good enough.
Get out your checkbook. I might be wrong, but I think Milledge is THE guy you go to if you want a 944 motor built to IT rules, and you want top drawer power, which you will need. he's very bright, and leaves no stone unturned. But that comes at a price. You will get essentially, an engine that is better than factory, and more powerful as well. Cost? Tough to say exactly, but it's easily beween 12K and into the 20s, if upi go Motec, etc.
So, is the 100 worth it?? Uhh yea....but it's the tip of the iceberg.