Newbie - Questions about converting lathe

Hi folks!

Just registered but been reading this forum for a while. For some time now I've been secretly plotting to convert my lathe (a Denford Viceroy 10x20) and my mill (an RF45 clone) to CNC, and I'm finally about to get started on the lathe. I'm also eyeing up my surface grinder a bit as it's bloody hard work cranking the table back and forth all day long, and it'd be cool to be able to grind tapers, spheres and so forth :)

I've put these projects off because I wanted to learn to scrape properly and make/acquire all the necessary tools and references so I could make the machines accurate before converting them.

Anyway, I've got the mechanics of converting the lathe covered, got all the necessary brackets and ball screws designed and sorted, but I could do with some advice on the electronics side of things.

Firstly, I'm a software engineer by trade and I'm extensively familiar with Linux, so I'm going to use LinuxCNC. I've even done some parallel port programming many moons ago.

I think on the basis of various comments I'm going to use some of those M542 type drivers as they seem cheap and well proven, right?

I'm confused about the break out board though. Can someone tell me what active functions it actually performs? By what means does a parallel port breakout board actually provide more inputs/outputs than the parallel port itself? And do I need anything special to use a charge-pump type feature with LinuxCNC? It's quite a big/powerful machine and I'm a bit wary about not having that :)

Also, to control the speed of the VFD on the spindle I presume a PWM technique is used to provide a digital simulation of an analog 0-10v signal? How is this achieved with respect to the signal from the computers parallel port to the break-out board?

And lastly! I obviously want a spindle speed sensor so I already rigged up a disc with holes in it to the spindle (inside the head) when I rebuilt the lathe. Does the BOB need something special to accommodate this or can I just wire it directly to an input on the parallel port?

Just a bit confused really as there's obviously lots of BOBs available and generally the adverts are poorly written or just far too short to explain everything I want to know!

Cheers for any advice,
Rich