Buying or selling your vintage guitar online can be tricky — especially at a time like this when prices are soaring. The guitar appraisal process includes: (1) finding the guitar’s model and year, (2) determining the guitar’s condition, (3) using the vintage guitars price guides and blue books, (4) checking reverb’s price guide and eBay sold listings, (5) comparing to live online listings, and then, (6) summing it all up.