You have only provided a generic description. Trying to put a value on anything with just this limited information provided is difficult. Value depends on a combination of many factors. Without a detailed description to include, finish, barrel length, overall condition, stock material, sights, box, original paperwork and any accessories, only a general estimate can be given. This weapon could be in the 100-550 USD price range.
100-300
50-350 usd
100-300 usd
100-350 USD
50-450 uSD
In Good Condition, September 25, 2007 = $310.00
50-500 usd
p90
Ruger has sn data on their website that you can check.
You can request a manual from Ruger on their web site.
$400-$500
100-350 or so