Do I need to degas my tank? - replacing big tank gauge

I have two gauges on my 9L tank. One little gauge below the bleed valve and fill line that always shows how much pressure is in the tank and another large glycerine filled gauge that only shows pressure when I open the main tank valve and the line is under pressure.
The larger gauge is the one I'm replacing. Since it is apparently not under any pressure unless I open up the main tank valve, can i pop it off to replace it without degassing my tank?
 
And be sure gage is at zero, unless that’s why you’re replacing it because it doesn’t read anything ever. You could also make sure the bleeder knob is unscrewed to assure zero psi.
Good to know. I'm replacing due the little plug holding the glycerine in the gauge popping out anytime I opened the main tank valve. Airmarksman sent me a digital gauge to replace it.