On my 2006 trek i have a suspension fork. it is a RST Gila T6 with the preload adjusters on both sides. If i overhaul this fork what kind of grease do i need to use to re-do it. Can i just use regualr bicycle grease, such as the one used in a headset? Any help would be appreciated.

You'll want to look at some sort of online manual for those forks or wait to see what is inside when you take them apart.. If they are just basic simple tubes with springs in them they may well recomend grease. But if they have actual oil damping innards you'll need to use the specific weight and amount of oil suggested in the manual.