Depending on condition, around $125.
Sturm Ruger still makes magazines for that pistol. They are the same ones used in their MK I variant and have a 9 round capacity. The subsequent variants, the MK II and MK III . They can be purchased on-line at the Sturm Ruger website, and are commonly available at gun shops.
You can get a manual for free at Ruger's web site.
You can request a owner's manual at the Ruger website.
Go to the Ruger website. There is a section to date your 22 by serial number.
Is it a revolver or semi-auto? You can go to Ruger's website to look up the serial number.
Ruger has sn data on their web site. 100-375 USD
100-400 or so
I purchased a new one for $37.50 New in the box!!
300 or so
very little market for ruger auto pistols, i would estimate 320 dollars or so depending on condition
10-200 USD or so