Do you know that you should either unscrew the working pressure's knob or T-handle almost all the way counterclockwise before you turn on the CO2? This might of been the cause as to why your Milwaukee's low pressure gauge got broken.
Whenever I remove my regulators, I reduce the working pressure down to 0 psi if there is some pressure left in the CO2 cylinder. If the CO2 cylinder is empty, I turn the working pressure's knob or T-handle until it is almost all the way out like I mentioned above. You can leave the needle valve at its setting, if your wish, while doing this. Then, after I have replaced the CO2 cylinder, I open the CO2 cylinder's valve. After this, I reset the working pressure and adjust the needle valve if needed. If you happen to unscrew the knob or T-handle all the way out, there is no problem. Just screw it back it a bit.
It is harder to break a two stage regulator's low pressure gauge than the Milwaukee's, but it is still a good idea to follow the above practice.