Matt,
Because it's plastic and still has the Indian head I would date it in late 50s up to '58 when it was mostly discontinued. Of course a dealership promotional program to highlight the Fisher/Pontiac connection. Due to all new bodies coming out in 1955 across the GM line I would say it's likely 1955.
When establishing a value you've got a few different groups who have interest. Pontiac collectors, sign collectors(those who like or don't mind plastics), and Promo car/dealer car collectors.
I would estimate it being worth $350-500 if there are no real cracks or damage and the color is not faded. Drop the value 25% if either of those are found on the piece.