How much is a 1937 gold 5 dollar walking liberty coin in MINT condition worth?

Not gold, and not 5 dollars. Gold coinage in the U.S. ended in 1932/33.

You have a gold-PLATED walking liberty HALF DOLLAR.

The good news is that the underlying coin is 90% silver so it's worth about $4-5 at current silver prices (05/2009)