The best place to both obtain information about visas and actually apply for a visa is actually G3visa.com. It’s really very user friendly. All you have to do is plug in your citizenship information and your destination and it will tell you whether or not you need a visa and how you can go about getting one. As far as international phone rates, you might wants to check what EKit has to offer (http://www.ekit.com/ekit/home/). They have international phone service programs that are created with travel in mind. Skype, a free international calling service provided by Google, is also a pretty cost effective option for international phone calls. Hope that helps!

You should check with your study abroad office regarding your visa to study in Ireland, as they normally help our with the paperwork and that.
If you don’t already have on, I’ve found that the ISIC card has great international calling rates from overseas. ISIC cards can be purchased at any STA Travel location. As well as great phone rates, they also offer discounts on airfare, hotels, sightseeing etc