I'm flying into Dublin early on a sunday morning, and I just wanted to know if I can travel from the airport to the Dun Laoghaire Harbor area without having to use a taxi. Bus? Metro? Any other alternatives?
There's a pretty good page about Getting to & from Dun Laoghaire, and from that, it looks like the bus is a viable option:
The first bus 41 on Sundays leaves from Dublin Airport at 07:15. How early are you arriving?
From the centre you can then take one of these towards Dun Laoghaire:
Some of these buses start between 7-8, some only at 09:30, and some don't run at all on Sundays. For more details, you could try the Route Planner.
Regarding the price: from the dublinbus.ie site it's not immediately clear if you can continue on the same ticket when changing to the Dun Laoghaire bus, but looking at the list of fares, it's going to be quite cheap in every case (compared to a taxi which would cost around €50).
Dun Laoghaire Harbour is a little to the South East of Dublin City Centre. The Airport is to the north.
The Dublin Airport Website has a great section on getting to/from the airport which you should have a look at. I don't believe there's anything listed there that'll take you direct, but it might be worth double checking!
The option that springs to mind is to take a bus then DART (local train). You can take the 747 Bus from the airport to the city centre, which runs pretty regularly, to Connolly Rail Station. From there, change onto the DART, and take it to the appropriate station. (There are two serving Dun Laoghaire, so go for the one nearest your hotel!)
Those pages are well out of date.
There is a direct bus from Dublin Airport every hour to Dun Laoghaire. It will work out much quicker than using more than one or two modes of transport.