If I had plenty of money but poor credit and not much time, I might consider paying someone to help me 'fix' my credit.
But if you have a bunch of debt, don't pay someone for something you can easily do yourself - you're much better off leveraging that money to deal with your creditors and pay down the debt. You need to be very organized, have a plan, and get promises in writing.
Many of these folks will suck you in telling you that they can settle your debts for a fraction of the real balance owed. They usually don't tell you how much worse this will make your credit, and how the IRS will come after you later for the written off debt - which they will consider income that you need to pay taxes on.
Learn the basics, the knowledge will serve you for the rest of your life. Don't make another move until you know what effect it will have. I had a high interest credit card that I paid off and closed, it really hurt my score for some time.
Some of the basics - avoid opening new accounts and especially closing really old ones. Keep any balances spread across multiple accounts so no single account has a high % balance on it. Pay everything on time and if you can't, contact the creditor immediately and work something out. If someone says they will remove something from your record, make sure you get it in writing - chances are it will come back months or years later and you need that letter to get it removed again. If you have positive history that is not showing up, see if you can get it reported fresh again.....