Yes, 100% safety first.
Here is the manual.
The 380DA has excellent wiring, using contactors instead of manual battery disconnect switches. The factory properly wired the output charging wires to the battery side of the contactor, so the charger would squirt into the battery, even when the contactor is set into the off position.
The safest old disconnect / new install method is to turn off the AC Converter, then verify zero AC shore power supplied to the device. I really like using a blinky / chirpy "sniffer" to detect AC voltage.
Then turn off all three battery contactors.
Then carefully remove, set aside to avoid electrical contact with any metal and especially any battery positive terminal, securing every single battery negative cable to prevent contact (all thick black battery wires). Verify nothing onto every single battery negative terminal (VERY important).
Verify 0 VDC from all three existing charger output wires (red) to ground (black).
Now the wiring is safe to handle.
Follow the manual instructions.
Remove the old charger, including the AC input and the DC output wires.
Follow the device mounting and the wiring instructions on pages 9 + 10.
Place the included temperature probe as instructed on page 11.
Select the battery chemistry type as shown on page 13.