Tom Mansanarez painting

I have an original Tom Mansanarez painting. Signed and dated 1981. I know it is a one of a kind painting. He was a friend of the family when he lived in California. It is a picture of an Indian on a horse. I have researched him on the net and found some of his prints are worth thousands. But this is an original oil painting. Can anyone direct me to where I can get an appraisal? Or anyone know a value of his early work? PLease let me know. I can email a picture of it.

Thanks! Julia