I can understand your nervousness. I went back to college to study architecture when I was 33. On the whole, it was a very positive experience. I thoroughly enjoyed it, it changed my life and gave me many valuable life experiences taking me all over the world. However, there were many times when it was not easy, financially or emotionally.
Firstly, I think you should seriously consider why you want to make this move. An art directors job, whether you are in advertising, publishing or film bears little relationship to that of an architectâ€™s. The architect may be romanticised in films but in reality it is a job that involves long hours and not particularly good pay, especially compared to other professions.
It is 5 years minimum (most people take more) and that is just to get your B Arch. Then you start at the bottom of the ladder in a practice, and have to work your way up. A couple more years and then you achieve your Part III, so you are probably looking at the best part of 10 years to becoming an RIAI Architect.
Secondly, you should think about whether you have the required qualities. Now, what they are Iâ€™m not sure. Off the top of my head - an ability to conceptualise, communicate, draw and open minded enough to work consecutive all nighters â€¦..( anybody else?). If you only have â€˜some tiny aspects of drawingâ€™, I would work on that. Maybe go to an evening drawing class. You will need a portfolio to get into any architecture school.
The two established Architecture schools in Dublin are quite difficult to get into, and also the first year intake is all 18 / 19 year white middle class, so you might want to look at one of the new schools (Waterford and Limerick) or at one of the 50 odd schools in the UK where there is far more diversity ( and places!). As far as I am aware, there is no part time study in this country but in the UK , some courses offer part II part time.
If you are prepared for all that, then go for it. It is very rewarding (job satisfaction wise) and I do not regret my career switch. You will meet lots of great people and come to see the world through different eyes.
If you want more information, you can PM me