Marvel Comic Book Values

I have a 1978 Scooby Doo Vol.1 # 6 comic's title fester and the buffoon, I found one on ebay but it is not for sale by tender. Does anyone know where I can look to find someone interested in buying this copy has been stored for nearly 28 years in a plastic bag, he is in good condition.

im not sure it would be worth that much because I have a comic book and 1972 are so u might want to Google or something