Ahhh, consider yourself lucky. Dusties are one of the best, if not the best, slayer assignments to get. Especially if you have the Slayer Helm. Wear strong melee armor, bring an inventory of fair food (lobsters are great), and buy some Bones to Peaches tablets if you haven't unlocked it yet, as these will allow you to stay as long as you need to. Also bring some alching runes, because they drop a lot of Red Dhide Vams and such.