It can be fixed easily. You can opt to repair or replace it. Start with referring to the online service documents
to help you locate the components and some videos
First remove the side panel
and locate the noisy fan.
If the fan on the processor is the problem, take care when removing
and replacing it. Incorrect replacement
may damage the board and CPU.
For all other
fans, try blowing air from a vacuum
cleaner with blower or a standalone blower.
If this don't
fix it, use a philips screw driver to remove the fan. Disconnect the power source and proceed.
Note whether the fan removes air or sucks in. It depends on the fans direction. Remember this or take a photo.
Remove the fan cables from the mother board but remember
to take a picture of wires in case you forget which
goes where. Or you can just point the fan
away from motherboard if the wires are long enough. CAUTION: Do not touch or remove unnecessary components. You may find it difficult to replace.
Look for a sticker on the fan (some have it on the back) and remove it, put a drop of oil in that hole and let it seep. This should be enough.
If the fan does not have a hole, use WD40 and spray it lightly underneath so it penetrates the bearing. Use a tissue paper to wipe excess. Replace the fan.