Most young children would naturally be nervous about hospitalizations, surgeries, medical equipment, etc. What's important is how you act. If you wince, flinch, act disgusted or grossed out, a child will pick up on that. If you convey that you trust the doctors and that this procedure or this surgery is going to make your child feel a lot better, and if you project an air of calmness and reassurance and trust, your child will pick up on that as well. That goes for anything - a vaccination, a tonsillectomy, a broken arm, or just a routine physical exam. You can't control how a child reacts, but you can control how you react.
It would be irresponsible for any of us here to give any type of medical advice or advice about how to deal with any issues of the medical kind.
But, there are some basic guidelines for helping a child who has had to have a medical procedure. If it's a one-time deal, like having tonsils removed, there's usually no harm in letting the child have a few treats or indulgences. Ice cream for lunch, watching fun videos during the day, etc. If your daughter has the catheter for a short time, say a few days post-surgery, you might consider asking her teacher for some simple worksheets to do at home. Besides the care for the catheter, she may be tired from surgery and anesthesia, and some rest at home might be nice. But again, make sure your attitude is positive.
If your child is going to need long-term care, or if whatever her medical condition is will likely be chronic, then perhaps she (and you) will benefit from help from a professional. Certainly your hospital/medical team can steer you in the right direction. Most hospitals have a team that can give support when a life-altering disease or condition is diagnosed.
Don't search the internet for medical care advice. Every situation is different. One person with a catheter can have a very different situation from every other person with a catheter. Ask your doctor, and if you're not clear on instructions, be honest.