Emac fan is sounding worse

I have a 1 Ghz Emac. The fan has been sounding different lately. In addition to the normal noise, there's a high-pitched component. It sounds kind of like water running through copper supply pipes, if you've ever listened to that in your house. Has anybody else had this problem? Is the fan wearing out, and if so, is it serviceable?

I should mention that the sound comes and goes. I'm assuming it's the fan. It's not the optical drive, so the only other thing is the hard drive. I do have my stuff backed up.

I don't want to put much money into this computer, since it's getting old anyway.

I wonder if it might need lube, or maybe it's unbalanced from dust buildup? I'm afraid to open up a CRT case though.

I actually have another Emac, but it needs RAM and I don't know if it's really worth buying that either. I might just look for a refurb Intel machine if this one goes.