So I bought my grandfathers 66 must convert about 15 years ago and have slowly restored it and taken care of it.
I frequently get people coming up to my door with $15,000 cash to buy.
I don't want to sell and don't intend to.

I have it insured; but I think that the insurance company insures the car for that much. They mentioned appraisal and sadly I have no knowledge on that matter at all.
Can anyone help?
Do I need to go to just any garage or mechanic or do you go to a specialized appraisal office (if there is one).
Is this a standard rate with a standard appraisal or should I shop around for what they charge (what is an average charge) and should I get a few different appraisals?

The car still needs work and though I have been offered that much money, technically on paper it could be worth less; but it also has the potential to be worth much much more.
I live in southern california
thanks for the help....
cheers,
Micah