We used this in September 2003.
An excellent service, much more relaxing than the main hall.
The price for turn ups is $20, the price through TCD was £10.
There is a website for the airport/lounge, do a google for it, I don't think you can book that way but you could get their number and take it from there.
I'd be tempted to just call TCD and see if you can book through them.
One thing to be aware of is that you will be called through to your flight about an hour and quarter ahead of schedule, so if you want to use the lounge to the full you'll have to be at the airport early. Sort of defeats the object but something I would do again, turn up early and beat the checking in queue, which was horrendous, and relax in the lounge instead of standing in a poorly air conditioned hall surrounded by others with glum going home faces. ;-(