Vostro 470 fan replacement

Hello,

I have a Vostro 470. There are 3 fans, one attached to the chassis with screws, one attached to the heatsink with screws and a third on the underside of a board that seems to be attached by plastic pegs (for lack of a better description). The fan on the underside is making noise and I need to replace it. Dell does not sell the fan and wants me to send the CPU to Texas for evaluation. I'm hesitant to do this.

Does anyone have any suggestions how I can replace the fan myself, where I can get the part or any helpful advice.

Thanks!

Art