Depending on how it's mounted, it might be easy. There's usually a peel off label on one side of the fan. Just peel it off and drop in a drop of fairly thick oil (e.g. Motor oil). Spin it around a little, stick the sticker back on, and you should be good to go.

But with the hassle in getting to that point, you might just want to replace it. Assuming you can get a part number or equivalent before you start the disassembly.

HTH. Good luck.

Cheers,
Scott.