We refer our clients to Jim or Kevin at Illinois Credit Services, Inc. http://www.illinoiscreditservices.com/. They are a fee-based service but I believe are much cheaper than Lexington Law and we've always had good luck with them.
Paying off collections can actually hurt your score in the short-term since it shows a current reporting date on a derogatory item.
Have you tried calling the hospital / medical profession to see if they will remove the collection as a courtesy since they are paid in full? I recently had a large suburban hospital remove 2 collections from one of my client's credit report as a courtesy. It raised his score from 575 up to 660 so he had no problem qualifying for an FHA purchase loan. I called on the borrower's behalf and only took a few minutes once I got transferred to the right person in client accounts.
You can also check out the website http://www.creditinfocenter.com/. There is a lot of clutter on this website and they're trying to sell product but there is some good free information if you can sort through the clutter. One method that I've seen work very effectively in the past is debt validation (it's a link on the left side of the webpage about half way down). You can click on this link to go directly to that section: http://www.creditinfocenter.com/rebuild/debt_validation.shtml. The idea with deb validation is that you challenge the collection agency to prove that they are authorized to collect the debt. If they don't respond within the legal time frame they have to remove the information. Most collection agencies are not going to bother responding if the collection has been paid in full since they've already been paid.
I hope this helps.