I have a wonderful Bernina that I cherish, but I would never buy a Bernette! The quality is simply not there. You can spend the same amount of money and get a much better machine in a Sears Kenmore or Janome.
You will love your Mom's Bernina!
You might want to spray starch the backing fabric before machine quilting again; it really helps with preventing puckers, especially if you are not using a walking foot. No need to iron, since the quilt is already layered. You can just spray lightly, let it dry, spray one or two more times, and be ready for quilting.