1) im guessing thats nothing really to do with the export function and could have been an accident. it will probably fix if you delete the single mission and then re-export it. if you want to discover the source of the problem you could de-pbo the mission and take a look. sounds weird
2) create a trigger with type end1 and put the following in the condition field after removing the "this":
!canmove truck1 AND !canmove truck2 AND !canmove truck3
the above lines assumes you have labelled each truck "truck1", "truck2" and "truck3". change either the above code or the names of the trucks to suit your needs.
also, you sound like you could benefit from the tutes in the ed depot. hop on over and take a look.