Warlokke, I'm far from an expert on used rifles of any kind - I'll defer to the experts on things you should check out first - but I gotta agree with our friends here about this one. $300 seems a reasonable price if indeed it's in as good a shape as you think it is. Especially if there's no rust or pitting in the barrel, the bluing is still sound, and the furniture is nice.
Have you tried cycling a few unshot rnds through it just to check of ejector problems? (That is, load a few rounds, and cycle them through without firing them, keeping the gun pointed in a safe direction (e.g., into the ground in the back yard) for safety.)
Given that my new one cost me $470 (and I had to drive two hours to get it), if it was me, I'd offer $275, but would probably still take it for $300 if that was rejected. My sense is, they're built so well, especially the older ones, that if anything minor is wrong, a smith could fix it up for less than you could buy a new one for.
Please keep us posted about your decision.
Nem