The state will probably have records of wells drilled in the last few decades. If it's older than the 80's, it may be hit and miss, but it doesn't cost anything to check. There are some things you can save money on by doing it yourself, but hardly any of them involve wells. Even if you figure less than minimum wage for your own labor, you'll be way ahead by getting a professional to clean it out. A pro may also have a downhole camera to check it out. If you start using hooks and improvised stuff downhole, you could end up damaging the well screen, and then you'd be calling a pro anyway to either plug it properly or drill a new well. I've been working with wells for 25 years, and I wouldn't mess with a well on my own property (if I had any property) beyond disinfection and pump testing.
Whatever you do, DON'T TRY TO POUR CONCRETE DOWN THE WELL without cleaning it out. Decades ago, I worked with a county program plugging abandoned wells. I went out to look at an old well on a guy's new property. He took the plywood off, and there was a hand-dug well filled to the top with old pesticide cans. I mean arsenic grasshopper bait old. I put the plywood back and said, "I never saw this. Call someone TODAY and get this cleaned out and properly abandoned." It was a voluntary program so I had no enforcement authority. The program was, however, funded by the EPA so I couldn't help him out without exposing him to potential liability. Had I been with the state water quality agency or EPA it would have been a huge problem. The thing is, if there is something nasty down the well and it is traced back there, you could be liable. Regulatory agencies will almost always work with you and cut you a break if you are trying to do it right. They don't want to write you a violation, they want the water protected. They really, really get annoyed when they find out later that you have tried to hide a problem. If you have plugged the well yourself without cleaning it out first, it becomes destruction of evidence. When a professional plugs a well, it is first disinfected, then filled from the bottom up with bentonite pellets to the water line. Depending upon the state, it can either be filled with clean native fill or cement from there up; the casing is cut off 3-4 feet below grade, and it is regraded. If you just dump bags of stuff down from the top you can get all sorts of bridging problems and leave voids, which can collapse later or allow contamination to travel between aquifers.
Call your county water conservation district or the local NRCS office, they have programs that may be able to help you out.