Some questions for those of up to date on the current motion hardware/software regarding Mach4

I have a 3'x4' CNC router that has been built and has been sitting dormant for well over a year. It was built around a gecko g540 and as far as I ever got was messing around with the Mach3 demo. I am now at the point that I have the time and can afford to purchase all the software I have wanted. Problem is, I have forgotten most of what I learned before. I would like to re 'learn' all of this and do a clean start with Mach4 (future proof) instead of Mach3 and I am trying to move away from the parallel port restrictions I can use modern computers.

My questions are:

1) What is considered to be the best options out there for making the Gecko G540 compatible with USB?
2) Should I bother trying to do this conversion or go with another setup, if so which one is popular for USB?
3) Provided you were in my situation (not knowing either of the software packages well), would you bother with trying to start with the new Mach4 or go with Mach3

Thank you-

Jason