Luthier school is a good option to choose... It will give you some solid crudentials and be a good foundation for a solid resume. However, according to my sources... its not neccessary. I've had the oppertunity to chat with a few pro guitar techs... I had a beer with Eric Sardinas' guitar tech after a show at the House of Blues... and I also had the priveledge of meeting Kirk Hammetts guitar tech for a brief moment. I asked them both the same questions and the answers were not that different. They both said that its not just about how you learned the stuff... its how good you are at it. You have to be able to give the guitar player(s) what they want. This doesn't neccessarily mean you have to be specially trained in how to do a set-up... just as long as you can do it right. The most valuable thing a guitar tech can have is experience. So do what most techs do... submerse yourself in the trade... work on guitars every chance you get. Take on personal clients once you get a feel for it... get some literature about the topic... Get your own experience. I've taken on clients and have a small list of people that I tend to... I haven't made a business out of it yet but I believe that I could if I wanted to... The only background that I have is an Engineering background... and a lot of time spent with my guitars... I've built guitars customized guitars and worked on my own guitars for the last 3-4 years and its helped me understand the instrument a lot better and also helped me develope my own skills and techniques of doing things... So I suggest doing the same thing.