what is fair price to replace something called the "oil pan" or "gasket Pan"?

What is your question?

oil is leaking out. first I went to independent mechanic & that's what they told me. then I went to Buick & they said there was no leak but oil was all over the place & to come back (no charge) if leak reappeared. I went back after observing oil starting to leak again & they said the something another pan (sorry I don't recall name) needed replacement. thank you.. I see the drips on paper I've placed in the garage under the car.