If you sell alcohol without a licence you will get into trouble, no matter where the beer came from.
A brewery license is fairly cheap, but that only entitles you to sell to people with a licence, like pubs, or offies.
That means that you will be trying to persuade the Irish Publican to sell your beer for you.
Setup costs are going to be building, plant and machinery, etc.
One of the biggest considerations, in my opinion, is packaging.
How is the beer to be packaged? Keg? Cask? Bottle?
What will it cost for equipment to package the beer yourself? How long will it take for you to package the beer?
Will you contract out the packaging to another company? Will the beer have to be filtered?