Hi mbj-
So sorry to hear about your sis. That must be really scary for all of you. You're a good sister to come to her side and seek out info for her.
The feeding tube is hopefully temporary. Is it a naso-gastric (tube inserted through nose) or gastric/jejunal (inserted through abdominal wall)? Be very certain that you aspirate (draw back the fluid from the stomach or jejunum) prior to pushing in any meds or fluids. If she is alert enough, she could possibly do this herself. Also, to prevent regurgitation, keep the head of her bed up at least 30 degrees. I'm sure the in-house nurse mentioned all this.
Stay strong and be a blessing to your sister and her husband. Are you going to the gyno for regualr exams?
Chances of a problem? Slim to none. I know of a number of families who deal with feeding tubes. Many of these tubes are even in children who were born with various physical conditions or disabilities, or the tubes have become necessary because of an injury or illness. The adults with feeding tubes fair better than the children, because children are...well... children, and they do things like put spitballs and such in their feeding tubes. Really.