I am an ex primary school teacher who took early retirement at 49 . You do need Grade C in Honours Irish as an entry requirement.There are post graduate entry routes as well.1.5 year course after completing degree.You still need the Grade C in Honours Irish for this course.Have you checked the Hibernia on line course,not sure of the entry requirements.
Some people do primary teaching in a college in the U.K.,come back and do an Irish exam to be recognised to teach in Ireland.
While the job seems attractive,short hours ,long holidays.It is a demanding job,mentally and physically.It is getting more demanding as time goes on. Remember your job will involve not only teaching but being a social worker,psychologist, PR consultant and many more roles .I spent 27 years on the job,20 years as a teaching principal.I am physically very fit ,can still run marathons in 2 hours 50 mins,I am now on a career change moving into the area of exercise and fitness.
Have you considered applying for the position of classroom assistant [Special Needs Assistant] .You would need to do a child care course for this position.By being in a classroom situation you would quickly get a good idea of the daily demands on a teacher.It would help you make up your mind about teaching.