About $300.
Depends on who did the engraving, and if the pistol has ever been fired
Zero. Ruger never made the P38.
Go to http://www.ruger-firearms.com/Firearms/PS-SerialNumberHistory.html. AFAIK, Ruger never made a pistol that chambered only 22 short.
You need to contact Ruger. You may have a prototype
200 or so
50-500 usd
Ruger has extensive sn data on their website.
You can request a manual from Ruger on their web site.
The link at the bottom of this page will take you to the Ruger website for your pistol. You can download the owner's manual for your pistol, which includes instructions on assembly and maintenance.
Ruger's website has sn data.
Request a manual from Ruger's website or take it to a gunsmith
You can get a manual for free at Ruger's web site.