if you got some good stuff like arctic silver or MG Chem silicone, great. if it's radioshack 6.99 special. not so much.
as long as the fan is not seized, it should be fine, they used a ball bearing fan in some of them so they get noisy, but still spin. if you peel the label off the back of the fan you can see if it's ball bearing or a sleeve bearing. sleeves seize up.