I got one of these and it has worked well for engine and tranny, have yet to do the V-drive, but that's coming soon.
http://www.skidim.com/prodinfo.asp?number=SUC01 It comes with skinny hose that fits down the dipstick on my engine, tranny and V-drive. You can generate a pretty nice vacuum with it by pumping it alot and then releasing the clasp on the hose. It's good to measure probe around in the pans to make sure it's as deep as it goes. You will hear it hiss when it's just about done.
Good rule of thumb is to measure what you take out and replace that amount, particularly on the tranny, then check it at the lake. I found I was right on the money with what the engine manual said. Changed fluids in under an hour with no mess.
You can do the tranny and V-drive cold, but the enine oil should be heated by running it for a few. You will need to get a garden hose into your cooling system and supply the engine with water before the raw water pump, otherwise you'll fry your impeller. Some boats have a fitting already plumbed in.