Advice on a Ruger P-90
 

So last friday night I go over to a buddies house to help him do some remodeling work and look at a motorcyle he has for sale. After we get done with the work and looking at his bike we go back into his house. He says that he is selling his Ruger P-90 and wants $300 for it. I think its a good deal.
I prefer something different and looking to either figure out the trade in value or what I could sell it out right to another buyer for... So let me know what you guys would give for the gun.
The gun comes with Factory Sights, 2 Magazines, holster, and a box of ammo.

Thanks for the help!