Your school should provide you with all the information you need regarding how to get this done. It sounds like a complex process, but is actually quite straightforward. If you look up the Omani Embassy's website they should have information on there what to do from Ireland. I found both the FO and UAE Embassy were really on the ball with this and it took no time at all - and that was all done via the post. If you are posting, make sure it is Special Delivery at the least!