JD 35d Problem

Good day to all. I have owned a JD 35d mini-ex for 18 years. It's a 2004 machine. It spent one year leased by the dealer to a golf course. I bought it on return with less than 400 hrs. It was like brand new. We did a lot of concrete work; digging footings, etc for a number of years. I think it has close to 4,000 hrs now. The engine runs great. The problem I am having currently is: It had the machine out on a little demo/clean up job. No problems. I loaded it on a trailer and took it back to the shop. I went to unload. Couldn't get it started, which is not the end of the world. The battery was apparently low, which happens. I was hot. Dropped the trailer, with the machine still loaded. I too the battery out and placed it on a charger. A couple of days later, I go out, install battery, (Stupid me) installed it and hooked it up backwards, ground to the hot and positive to the ground. Couldn't get it started. Got mad, not even realizing it was hooked up backwards. Next day I go over there and notice my mistake. Pull the battery. Place it on the charger. Next day, battery acts weird. I take battery to the O'reilly's. They hook up and test it and say its fine. I take battery back and install on the machine. It starts fine. But, with the machine running, safety lever in position, the machine will not move or operate. This is my current problem. The machine will start, but cannot get the boom to move &/or will not move. Sorry for the long drawn out explanation of my lack of knowledge and my obvious stupidity.