Owner’s Manuals and Service Manuals for Guitars and Basses.
1) Most Yamaha guitars come with a small pamphlet that shows the direction to turn the truss rod to adjust the neck curvature. A diagram may be shown to adjust the tuning key tension if fitted with adjustable tuners. Detailed manuals on general guitar maintenance are not included but documents are available from the faq download site that will cover this.
2) For acoustic guitars that have preamps there are service manuals for the electronics.
3) For electric guitars and basses there are service manuals that have all the parts identified by part number and description.