I'm afraid i'm on the wary side too. I had a chiro to my mare a couple of years ago, just for a general checkup. She found loads wrong with her, treated her and it went downhill from there and it was one thing after another, she treated her and put stuff out that wasn't out in the first place! I ended up having a vet out to get painkillers and then had a physio out. I've never looked back and have the physio out every 6 months now, she knows my horse now, works closely with our vets and won't treat unless needed.
I'd get a second opinion.