Would a 1999 or 2000 3.4L fit in a 1997 transport Montana if so is therer any changes that need to be made?

Any 96, 97, 98, or 99 3400 SFI engine will fit. This includes from a 99 Grand Am or Alero or other GM vehicle that uses the 3400. The 2000 and newer versions are not a direct fit; I believe because of sensor differences.