6"? 4"? Box/Papers?
Worth? To a LGS, maybe $500 on trade. To a private sale, $750+.
Some people (like me) love the pony and will ante up depending on condition, age, accessories, etc. Others... meh.
ETA. a Colt for a Glock? I'd do it. The 357 is closer to your 9mm family, just a little longer and noisier.
A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government." - George Washington, January 8, 1790, First State of the Union Address