New User and Visitor to this forum. Greetings All!

So we purchased a Pro4896 , so far we love it. This is also my first CNC so please bear with me if any of my terminology is not accurate.

Moving along to my problem,
I have a PC that is running Mach4, occasionally this PC will crash (I'm working on fixing that - this isn't the problem I am coming to you all for help with). When the PC crashes Mach 4 obviously closes out. When I start back up the G-code is gone and I am not confident in the machines position, or where it left off in the g-code.

How do I go about picking up where I left off on my work piece in the CNC? (it is really frustrating to have spend 8 or 9 hours of machine time to have this happen and to waste that material and time! - yes I know get the computer fixed! )
When Mach 4 shuts down does it loose positional data?
Do I need to re-home and reload work piece X,Y, and Z zeros? Or is there an easy fix? If i have started machining my piece placing the XYZ touch-plate in the same spot is obviously not going to work as there will have been some material removed at least in the z axis if not others. So how do I compensate and correct this? I assume i could home the machine using the buttons in Mach 4 to zero out then record the material XYZ offsets on paper to input later on if the machine/ PC crash again - where would i find that data or offset or how would I go about applying it?