The Credit People offer a simple way to check out their services: pay an initial fee of $19, which includes your credit report (a service often not provided by credit repair services) and see what you think for the next 7 days. If you choose to continue using their credit repair plan, you'll pay a flat fee of $79 per month. The service can be cancelled at any time, and an "Unbeatable Satisfaction Guarantee" allows you to get a refund for one month's service fees (this is assuming you cancel as soon as you're unhappy, not months after the fact).
If you find information that is incorrect, you can file a dispute. Remember too, that items on your credit report that you don't recognize could also be potential signs of fraudulent activity — someone working to secure credit in your name for their own use. Make sure you're clear on items that could potentially be fraudulent, versus those that may simply be inaccurate.