Removing high pressure gauge

This may be a silly question, but... I just got a kegging setup that included a single body dual gauge regulator. I also got a CO2 tank from CL with another similar regulator. I've read that the two can be connected to make a dual body for serving or force carbing at 2 pressures. Questions:

1) how on earth do I get the high pressure gauge off? I tried hand and wrench in both directions (assuming left and right handed thread). No dice. Also started trying to unscrew the small screws on the back of the gauge. This didn't seem right either.

2) do I need any other parts, nipple, etc to connect the two.

Tried searching and couldn't find this info

Unless the regulator is assembled with white Teflon tape the manufacturer used a liquid sealer to attached the fittings & gauges to the regulator body. If the manufacturer used a sealer then you will need to hold the regulator body with a vise while loosening the gauge.

And BTW we use Loctite when we assemble the regulators & manifolds we sell. We use high strength for all but the gauges and low strength for the gauges. This is because white Teflon tape is not rated for the high pressure side of CO2 regulators.