I rebuilt my M20 2ltr block myself a couple of years back so I know a fair bit about it. I can give you as much detail as you need - no problem. I gotta ask though, would it not be easier/cheaper/quicker to get another engine? My block rebuild cost £1200 UK, I could have had a decent engine for £300 or less. If you really are set to rebuild then give me a shout. Have you got somewhere you can keep the car while the engine's out?
Cheers,
Shaun