Q: Hello how long would it take to replace the oil pan and what would the cost be if I purchased my own oil pan

I took my car to a mechanic who wanted to charge me $800 to replace my oil pan but I purchased the oil pan myself I gave them $100 to hold my car because I had it towed there they also told me the work wouldn't be started until half was paid I found someone who would do it for lesser price the person who has my car called and asked what I was gonna do about my car sitting at their shop I told them I was on my way to pick it up when I got there with the intention of paying only a storage fee balance there was a wet puddle of oil under the car where the oil pan fits onto the car pass. side front they told me the work had been done but without my knowledge or the half that was agreed upon. They are trying to force me to pay them the remaining $700 for work they obviously did before I got there which only took me an hour because I stopped to get the remaining supplies for the other person. I just need a quote for small claims court. Thank you for your assistance. My car has 179000 on dash.
My car has a manual transmission.