Hi Stitchlips,
Yes you will need a driver, a component that goes between the computers printer port and the motors. It takes the pulses of info from the computer and tells the motors which way, and how fast to move. I'm new too, January, 2006 and it's a cool invention and mach is a great way to pull this off, I still have my share of problems but the more mach tutorials you watch and topics you read on this web , the more comfortable you will be with this subject... The support group w/ mach is awesome, lightyears ahead of my understanding of cnc machines, and although I jumped in here, ( blind leading the blind type of deal) If this doesn't help you, just re-post this and I bet someone else will help.
Good Luck with your sherline, Glenn