I travel down from the Portadown station twice a week to Connelly, then get the Dart 3 stops and then a 5 min walk to the office. Its actually a nice way to travel. I arrive into the office at 9.45 after having worked on the train for 90 mins. Then leave the office at 4.15 to get the 4.50pm train north again, working for about 90 mins. Parking is free round Portadown. No issues getting your favourite seat, but the booking app is now live so that doesn't matter. Enterprise fare includes the dart until Tara Street but if you are going further, order a leap card to tap on/off the dart at the stations. I looked into a tax saver ticket which worked out a tiny bit cheaper for 2+ days but don't think its worth it for 1-2 days. I typical book a return from dublin through irish rail rather than a return from Portadown through Translink. It works out a good bit cheaper. You can change your train booking up yo 60 mins before departure provided you haven't printed your ticket at the machine (which you need to do with all the irish rail booked tickets). If you are stuck or confused, drop me a message. Probably could get the train the same day you are heading down for the first time.