Nothing to worry about. I was 63 when i had a non reversible ileostomy and done great and now 70. Take things easy for around six weeks and do as told. don't over do things that's when problems occur. Same with regard to exercise etc. Eat little to start and build up food intake over a period of time. Drink stacks of clear fluids excluding tea/coffee/alcohol and aim for around two litres daily, Attend outpatients appointments and ask all the questions you want don't hesitate. You can also asked to have regular checks with a stoma nurse.
Best of luck, take care.