Here are some tips to help you on your way

1. Ireland uses the Euro while Northern Ireland uses the British Pound. Use a credit card with no foreign transaction fees and eliminated the need to use cash. Credit cards are accepted almost everywhere. Always pay in the currency of the country you are in. That is if offered the choice of paying in US dollars or Euros always pay in Euros, to avoid double conversion. US dollars can be exchanged at any bank but the conversion rate will be well below official  rate. Also never convert money at the airport. The rates are terrible.

2.If you want to use your cell phone while in Ireland just visit any phone store such as Vodafone or Three and they will give you a new SIM card to use while in Ireland. They will switch it out for you or give you a new ESIM. Usually costs around $30/month. Remember your phone must be unlocked to switch out SIM cards. Check with your carrier before you leave. Alternately you can get an international plan from your carrier before you go.

3.If you need direction on your phone before  you leave the airport and before you get internet on your phone, simply use the wifi at the airport and put the directions into maps before you leave the airport. The directions will stay in maps even without internet. Just be aware you cannot change the directions on route.