If I didn't have the specifications for the motor I was going to use, I would just put it in place and print a calibration cube. If the measurements are correct, I would leave everything alone. (And it is very possible that is what happens. Most NEMA-17 stepper motors have the same number of steps per revolution). If the axis where I put the motor is too big or small, I would scale the number in that line down or up (respectively) to compensate and print another calibration cube.

Also has anyone else been successful in upgrading their firmware to the most recent one? I am wondering what other changes I would need to do or maybe there's isn't a way atm?
The only thing you might want to do is use a visual diff program to compare your old configuration.h file against the new one. (and for that matter, configuration_adv.h also!)

Some of the names have changed. You won't have a hard time crossing your settings over. But you really should use a visual diff program to make sure you see the changes. Something like Notepad++ is good. Or ExamDiff Pro is really nice!