Hi.. I'm no expert. I've been twice, mostly in the north. There are several people here that actually live there and others that have lived and loved there, I'm sure they will be a fount of information.
I wouldn't drive.
Most of the roads are narrow and people drive at breakneck speeds, on the wrong side of the road... through a maze of high stone fences or ditches (as the Irish call them). I found traveling on the local double decker tour buses from town to town and cross cities easy, convenient and fairly inexpensive, but there are also cross country buses and in some places trains. The ferries are great and meet up with service on either side of the channel.
Definitely go in the summer. The weather is always iffy but it's a worth the wait for sunny days. Mind you, you can drop your camera and still get stunning shots on the worst of days.
You must visit the Antrim coast, Belfast has stunningly beautiful architecture and the "troubles" tours are fascinating. The Mourne mountains... I have a bunch of pictures under my profile.
I found the internet hard to find. Maybe I was just unlucky, I was staying with Relatives and due to a series of unfortunate circumstances I was unable to connect with any regularity, or maybe it really is that difficult..
Ryan air is cheap, but, BUT, they'll charge you for everything, last I heard, toilets were coin fed.. lol.. so it all works out even in the end. If your going to hop country for a few short day trips, it might be worth your while though.
Don't for the love of god, go to a bar, get drunk and start taking religion or politics. Just don't go there..
I've been to the south, Wicklow mostly. It's different than the north. Not as many stone walls, softer hills.. It's a beautiful country. I'll come back with some travel sites that I visit. They'll give you ideas on B&B's or hotels.
There are, as I've said, many experts on this site who hopefully will pop in and set my story right,
I hope you have a great trip.