Proceed to the Precision and Target Rifles EE, search "Tikka ctr". 24" barrel, assuming the round count/condition is accurate you've found your rifle...the lack of a meaningful trader rating, would make me a bit uncomfortable, but it is a tidy looking deal. A new one isn't that much more though.
*edit* You could see if the guy would send it COD, doesn't look like it adds too much to the cost, and takes most of the risk out of the deal, assuming the Posties will let you open the carton before parting with your money.
The Gear heads here will have you dropping several months worth of Mortgage on a set up, they're right if you've got lots of cash to burn. If not purchase above today, that will leave you with a nice chunk of change for a scope and the other accessories that are required. That will get your feet wet, shoot a few matches, if it's what you're after, then get the $600-$1200 Chassis.