yeah its all a gamble. but if the engine sounds good (right from ice cold startup). and it looks nice with warranty and papers, then you really cant ask for more than that.
as others have said, any original motor is also a gamble, or its been rebodged and no one mentioned it. and with 3000 solid km's I'd say its safe ( or fried already due to poor run in, but that should be noticeable anyways)
even buying a new car is as much of a gamble with the way they pump them out of the factories at low budgets atm......the number of current shape falcons ive seen on the side of the highway, or getting hoisted on a tow truck is bad. i'd be pissed if my brand new car did what a second hand one might do .
good luck