I'd suggest reaching out to your county extension office.
They usually have a person on staff to help you with both amendments to your area specific as well as where to send for testing. They usually work with one of the universities in your state to offer a reasonable cost testing service and then you are usually given a report back via email that indicates where your soil is at, what is needed to be added, application amounts and how often this should be done and when to retest. It does help them if you will let them know what you are growing in the soil. If you need to borrow a probe to get your samples pulled, usually it's a deposit and returned to you at return of the probe.
The cost to do a basic soil test in my state I think was $17-21. You can add on specific things to test as well that may not be as common to your area (such as calcium, salts, magnesium etc). Usually you receive test results in 4-6 weeks depending on their work load. I did mine in fall and amended over the winter. I'll be retesting this fall to see where it's at. The nice thing about the state testing is they know what the soil is throughout and know how to remedy problem areas. Worth a look at their services in my book.