Not difficult if you stock the stuff already and no dirt is in the line, etc. Since you don't know and don't have the stuff and don't know the precautions to take when removing the broken head and nozzling and so on leave it to the pro.
Next question is why or how did you break it? Stuck in the up position, not installed properly, etc.?
Don't let them nail you for damage on a poor install or malfuntioning head.
You know you mow across good heads all the time with no problem.