The "factory manual" is the DVD sized Rep-Rom disc.
Try to get the latest version no matter who you purchase it from.
This was the only source for a couple of years, until the Haynes
publishing company did their hardcover version in print
in the typical Haynes style.
Ideally, you should have both.
One for reading at work (the disc) and the other for reading in the library at home (the Haynes). Don't worry, you won't likely get so motivated by it nor intrigued by it that you will forget to flush.