Hello,
I would just like to caution everybody before using Orion Blue Book for getting guitar values. They are one of the companies that provides online blue book values for many products. I figured I would just check and see what the ballpark figure is for my Michael Gurian made guitar. As it turns out, my guitar is worth $270 in MINT condition.
Considering my guiar is only good to excellent, is anybody willing to pay $150-$200 for a used Gurian? 
I understand they can't possibly have accurate values of everything, which is why I caution you here. If you have an idea of an instruments worth, don't bother with Orion Blue Book. If you have no idea, then REALLY STAY AWAY FROM orion blue book. I find Ebay and local dealers to be a much better source for information.
Cheers!
John