Just in case anyone else is thinking of this... what you should have done is to take the Tung Chung line (also from HK station in Central). This takes you to Tung Chung which is just on the north side of Lantau Island inland from the airport. This costs less than HKD 12 each way on an Octopus card (maybe HKD14 otherwise). Then you can take a bus direct from Tung Chung to the Monastary for about HKD10 each way. It might not be quite as quick or comfortable as a taxi, but you get more of a feel for the local style.

But by far the best way (not the quickest) in my view is still to catch the ferry from Central to Mui Wo (Silvermine Bay) on Lantau and then take the bus from there. The ferry costs about HKD25 depending on whether its a fast one (30 mins) or slower one (about 45 mins) and whether its a weekeday or weekend. The bus meets the ferry and then takes about a further 30 mins to the monastary. If you're lucky yo can get one of the slow ferries that has an open deck upstairs at the back and sit out in the sun all the way over.