Chad
I'm no expert on this matter but I guess it would be quicker and cheaper to sort the rs port out and run it with the original control. I've got a old Bridgeport boss that I've swapped over on to the Mach control but I don't think I could have done it without the help of hillbilly who I got the break out board off, he suppied me with instruction which made the process dead easy. I swapped over to make the machine easier to use and to be able to run decent length programs, the old boss was very limited in memory space.
A break out board can be just a simple board with wire connectors and a db25 plug to connect your PC's printer port to your machine, some boards are a lot more complex with opto isolators to help prevent you frying your PC if something goes wrong, have a read of this it explains why you need one
http://www.campbelldesigns.com/breakout-board.phpAs far as I know Mach can control any motors, it's the drivers that are the problem you'll have to find out if they accept step/direction signals or something else, I don't know alot about servos but I guess they have encoders for feedback and I haven't got a clue about what happens with them.
Cheers
Chris
P.S. Just had a look at your website, freaked me out a bit, same age, same surname, same initials, love my bikes and I'm just starting to try and set up making bike bits to sell. Freaky