slimy oil change

What is the name of your state? Arkansas
I took my car to a quick lube and asked for an oil change. Within miles the differential locked up. Towed to dealer, and mechanic said diff. had been drained. $2000 in damages. I returned to the oil change shop and owner confirmed that mechanic had 'accidentally' drained 'some' of the transmission fluid, but was replaced. They are denying any liability, and deny touching the drain for differential, but dealer mechanic has said he'd testify to his findings. Oil business is now up for sale! I'd like to represent myself on this, but realize that if business sells before action, then new owner will not be liable, nor will present owner have to disclose. What steps should I take to make present owner disclose to purchaser that there is litigation pending. Also, if I go to small claims and win judgement, can I then place a lien on business? Thanks in advance.