There were 2 volumes of the original factory service manual for 2000 mustang.
There may be specific parts of the manual that call for you " see " other specific material. 2001 Ford Mustang OBD II Powertrain Control & Emissions Diagnosis Service Manual , sold separately from the factory service manual. Also I believe that there is a 2001 Ford Mustang Electrical Wiring Diagrams Troubleshooting Manual sold separately.
If some pple have more than 2 volumes I would ask what books are included.