Mate,
I've been 4 times - always a good time (apart from the weather on a couple of occasions).
Great people, great atmosphere, mostly great boozers, great racing.
Can't advise on ferry routes, as we've went via Troon the past 2 trips and since you're on the shandy side
of the border, there's probably ports within easier reach. Try booking with Billy Nutt - we got a huge discount last year and they were easily the cheapest we could find.
Accomodation - take your pick, but book as early as possible. Remember, the circuit is 11 miles long, so where you have your digs will probably have some bearing on where you spectate from.
There were a few new hotels being built on the coast section of the circuit last year, must be worth a try - sit in the bar between laps!
Take a good sized wad and have a belter of a trip mate - ride the circuit sometime before race day too - and take your favourite most comfy walking shoes - you always seem to walk further than intended there.
Be sure to visit Kelly's (biggest night club in N.I.), grunters (really called shunters, guess why), the anchor (in port stewart) and the harbour bar.
You'll have a great time!!
Cheers!
Scott