I was the one who did all that swapping a few years ago. So far the thing runs great to this day.

I managed to resurrect a 2.5ghz CPU set that I bought off ebay that leaked. Took a toothbrush and rubbing alcohol and scraped at the boards getting all the residue from the leakage off, then replaced the LCS with some normal active cooling heatsinks. Worked great and the damn things even Calibrated to the new board! I got lucky as I never previously had any luck calibrating CPUs. Most will just error out and I never found a fix for it. Changed fans and all and the same error kept popping up.

Maybe there is a CPU set for the cheap you can drop in. But beware, the fans will run at full bore since they need to be calibrated using the Apple Service Diagnostics CD. Even though, you are running a 50/50 chance they will even calibrate correctly. (Yes, you can attempt a calibration using the other heatsinks as my 2.5s calibrated just fine.)

Mileage may vary, but I got tired of the whirling fans and replaced all of them with some silent 12v fans going straight to the power supply.