You are completely numb when you have a root canal treatment so the process should be painless. It is quite common to have a little discomfort for a week after. Pain relief could involve taking paracetamol (dependent on your medical history).
The main advantage of root canal treatment is that you get to keep your own tooth rather than have it extracted.
Patients can be anxious about the prospect of having root canal treatment carried out but the majority are very surprised at how straight forward and painless root canal treatment can be.