. hello!
. that's a lot of questions !

. check out
http://vjforums.com/showthread.php?t=36211 (and vjforums.com in general) for a lot information on projection mapping.
. to start ? plug your mac into a projector, aim it at the wall and play around with the perspective transform effect (found in Modules-Filter(layer) ) and have it. see what works and what doesn't.
. for outdoor, building projection mapping - you'll most likely need to rent a high power (>6000 ANSI lumens) projector... for interior stuff, almost any projector will do - you'll just have to make the room pretty dark.
. good luck!
-james
(a nomad. )