Please help...I need legal advise ASAP:

I am trying to find out my legal responsibilities...if any....for a used personal vehicle I sold a couple of days ago to a person here in my city (Tulsa, OK).  I sold a 1986 Mazda pick-up truck (for $1,200) to a woman and now she and her elderly mother are calling me demanding her money back and threatening to "take me to court" because of some mechanical problems that arose a day or two after she purchased said vehicle from me. I did not give any written or verbal or implied warranty on the truck. The mechanical issues that arose are not major but just electrical malfunctions. The truck has a very recently rebuilt motor and a huge list of new parts and brand new tires, etc. It is running fine at this time by the way.

The woman and her mother constantly call me and scream and threaten legal action against me if I dont refund the money. They even went to my mother's home to do the same. (I had the truck parked in front of my mother's home when I sold it because my mother was having a yard sale and I thought it would get some good viewing if I parked it where many people were coming by) Then today I had the misfortune of being in the same grocery store at the same time these two women were there. The mother of the woman who bought my truck proceeded to scream at me in the store and threaten me with a lawsuit non-stop all the way out of the store to my car. Very embarrassing to say the least. She was accusing me of deliberately selling them a vehicle that I "knew had mechanical issues that I didnt disclose". NOT true by the way.

My questions are ..........Do I have any legal obligation to refund her money and take the truck back? And, if not, what legal recourse do I have to stop them from calling and harrassing me or even showing up to do so in public or at my mothers home or my own home?

I am pleading with anyone to advise me ASAP about this issue so I can rest and not have to deal with the horrible accusations and threats any longer. And also if I know my legal standing I can have a much more informed conversation with them about what they can or cannot do in the future by telling them I HAVE sought legal advise and it is as follows.....!!!

Please feel free to email me directly at    michaeljoe888***    I am desperate to resolve this issue!!!  The harrassment wont stop until I do so.

Sincerest thanks,

Michael