I've just given my buggy it's first run and it ran great - no stalling (apart from when it ran out of nitro) and smooth acceleration, but there was white smoke coming out of the exaust and afterwards the exhaust's end was wet- is this anything to worry about?

No, when breaking in the motor the car is running rich which produces alot of smoke. It should be wet because that is either the raw unused fuel or oil coming out of the pipe.
Good Luck witth the new car

ya its normale for the white smoke and the oil ans gas in the pipe but remember to put after run oil after u drive it and its always a good idea to have it at BDC (Bottom Dead Centert) after a run.[8D]