afaik, from the arrival area, u-turn ka sa kanto nung airport road going to roxas boulevard. go back to the road going to sucat, and you will see duty free at your left. just take the next u turn slot there. i think the next u turn slot there is before reaching multinational village.
Actually, on the road to Sucat from NAIA Terminal 1, there's a left turn straight inside Duty Free Mall. Also, they're open until 2am for the whole month of December 2008.