Blue Book of Gun Values has a store brand chart. 100-260 or so
Depending on exact configuration; a few hundred to multiple thousands.
100-300 USD
Anywhere from nothing to multiple thousands of USD, depending on EXACTLY what you have, condition, accessories, box, manual, papers, etc..
It depends on the quality of the gun. I am a collector and if you give more specifics, I can give you a better value.
50-200