Yes, you need to inform the PB that the projector is there, detect displays does that.
S-video works OK, but is in black and white sometimes, something to do with differing pin allocations in the plug I think.
The resolution depends wholly on the projector, we get 800x600 off the £2k Sonys we use at the Uni, it's OK for a powerpoint or 2, but gets crowded with ProTools or FCP running.
More expensive projectors get better resolutions.