In JAA-land, the requirements for differences training differ from one National Aviation Authority to another. In my experience, the ATR42-300 to 72-200 differences course consisted of 25 pages of theory (diagrams etc), a 3-hour ground school (done in half the time) and one 4-hr sim session (again, more than necessary). The whole idea behind the two marks (and two sizes) of aircraft is to keep differences to a minimum.
Fuel planning-wise, a ballpark fuel burn figure of about 550 kg/hr for cruise is about right for an ATR42-300 in ISA at FL180/190. My outfit uses 50 kg as standard taxi fuel (except at CDG where it's 170 kg). Typical TAS is 270-280 kts.
Cheers
