You can find several SKS sites online. Tuco's Forums has an AK/SKS forum. www.mosin-nagant.net
Russian SKS with the blue bolt is a rebuild. They're running $200 these days at gun shows.
The other gun is worth more IF you have the issued stock. Modified stocks decrease value, as does the missing bayo lug. Bayo's are legal on the SKS.
Russian SKS value comes from having all matching serial numbers (stamped, not scribed with a marking tool), stock parts, not a rebuild (blue bolt, laminated stock), sling, complete tool kit and cleaning rod.
Arsenal markings of origin are important. Tula (star) is not as rare as Ishvesk (triangle with arrow).
I got an all matching, unissued Romanian for $175 with sling, oil bottle.
They're great guns! Cheap to shoot, accurate, lethal. You can get $200 for them. A complete, matching Tula will bring maybe $300. Ishvesk a bit more.