Hi.....I'm a newbie too, probably the nubiest of nubes you can get.......so for what it's worth and my 2 pennnoths worth.....when you loaded up the software to get the machine to run you would have loaded the XML file to your hard drive too.....where it should still be.
Go onto your C drive on your computer and look for the XML file, which should be resident there and wouldn't have been altered at all......as far as I know.....if it's there DON'T MESS WITH IT.
You can't run your machine if the XML file wasn't there originally, so you wouldn't have gone into it and messed with the program..
AFAIK....the settings for Mach 3.....that you can set-up for your machine....... are in the Mach 3 config and you can set the parameters there.
BTW.....the home position on a CNC router is at the bottom left side of the table....that would be X0 Y0......but the work offset position is the starting point you set for your particular work piece with G54 and is X0 Y0..... and can be set on the corner of a vice or anywhere on a work piece that you want to machine from......Mach 3 doesn't know where the spindle is unless you set those points yourself.
Ian.