Go to a gun store or book store and look it up on Blue Book. That will be close. But gunbroker, gunsamerica, or auction arms will give you a good guess also.
If you buy it new, Plan on around $150-175 at a local shop. Used and in good condition, around $125 or less. It will depend on the person your buying it from and what your will to pay. If your going to Gander Mountain - well I wouldn't go.
I have notice that gun prices have come down a few dollars in the last few weeks as the market has slowed.