If it's been ridden, and assuming it's fork oil, there should be a fine spray on the timing cover, and a trail down the forks (and you want to be sure your brake pads are not oiled). It will be thin and may not look red on the timing cover, wipe it with a white cloth and see if it looks red.
Then get a Seal Mate (OK) or Seal Doctor (much easier to use).
http://www.amazon.com/Motion-Pro-Seal-Mate-Cleaner/dp/B0039LDF4Ahttps://www.youtube.com/watch?v=8wlzfoVroSYhttp://www.riskracing.com/pages/Seal_Doctor_Page.htmlhttps://www.youtube.com/watch?v=W3Re9wpdNFg