Newbie Setting Homing Limits and switches

Hi,

I am new to mach 3 and have been watching video tutorials. I have noticed that the sample g codes are engraving very small like they are in mm even though I have the system set up for inches. I was wondering if this was just the way the g code was written and since it came with the software it couldn't be changed. Also, the homing switches in the diagnostics panel will not turn on. I am pretty sure I have followed the directions thoroughly but, am still not having any luck. There are also times when the spindle will also not turn on but the axes will follow the tool path as if it were. I have tried turning the spindle on manually and then running the g code but that doesn't work every time. I would appreciate any suggestions you may have.

Thanks