Printer head overheating message, etc

Hello, I have three Epson PX650s in various states of repair. (I like these printers better than the models which replaced them). OK, printer 1 is the "most" working - this prints perfectly fine in normal mode, but in high quality mode, or CD print, it makes a grinding noise and jams. Also scanning is noisy. Printer 2 was working OK until recently, now suddenly showing a "print head overheating" message. Printer 3 is the most dead -this comes up with an error message as soon as the power is turned on, just gives one click then stalls. I'm perfectly happy to spend some time taking them apart and have the instructions and the diagnosing program. What would the experts' advice be? To replace printer 2's head with one from 1 or 3? Or to replace 1's mechanical parts from one of the others? Or is 3's start-up problem likely to be something simple? Any advice appreciated. Thanks, MD. (PS - it seems to be a kind of tribute to this model that they are now selling on eBay for more than they were when sold new!)