if u separate all of the compressor wiring connectors , move the compressor wires out of the way, install a new fuse, start the landy, then see if u have power on the wiring loom side connectors , if u do then it should indicate the loom side is ok
if u remove the compressor the suspension will indeed discharge and the landy will drop to its bump stops, u could try quickly putting 12 volts directly to the compressor but imagine it will pop the large fuse
a new relay should come with the new compressor , if u replace it with an AMK one u need a software update
however u won’t know the system is working 100% even after u fit a new compressor, as there could possibly be a bad wire further up the line , height sensors etc , in theory it should just be the compressor but u never know seeing u haven’t seen the system work yet, hope it hasn’t damaged the ecu , but the fuse should have protected that
will just be the case of starting with the compressor and working ur way through it bit by bit
there is a chart showing which wires or what on the compressor, will try and find it for u
if u do end up fitting a new one u will also need 2 x pushfit connectors for the plastic pipes on the end of the compressor