Prior to servicing, we recommend shutting down the OS, switching off the ATX power, and unplugging the case. Then install any stepper motors, end-stop switches, and machine specific modules. Note, some laser-modules available to the public have an unsafe default ON-mode, and thus we recommend following some extra precautions noted in the machine wiring diagram plans.
Also, a complete dust-cover is highly recommended around machines that generate metal filled grinding dust or milling tailings.