Yes, the broken pieces still have some merit. The barrel of the sheared hot end is the only thing that is not any good anymore. Once you remove the sheared piece from the nozzle, it's as good as any other nozzle. You'd just have to clean it out with acetone. A good heating with some fire (either a torch or gas flame from a stove) will help to clean out the remaining plastic. You can quench the heat of the nozzle in a small bowl of isopropyl alcohol (ventilate the area when doing so) which will evaporate once you remove the cooled nozzle from it, leaving no water behind.
The PEEK is still good. You would need to remove the barrel and replace it. MakerGear sells barrels for about ~$7.50 + shipping. There doesn't need to be any heat for this, but you do have to be a bit slow when you remove the barrel. if you want, you can heat the barrel a little to give yourself a bit of a start, but mine unscrewed pretty easily.
The thermistor and heater block from the second one are still good. The block goes back on the barrel first and the thermistor just needs to be re-attached to the nozzle after it's in place on the barrel.
The only change you have to make is to let your slicer know that you're using a different sized nozzle diameter. Slic3r has it in the printer settings configuration area under Extruder1 . So once you change it there the changes will carry though for all your slicing. You may want to recalibrate flow rate, but it's a simple process.
Rocketman wrote: lol. I will learn all I can, but with things breaking all the time I can't be sure when my next lesson will be. lol.
We're all the same way when it comes to the "infernal machine." The important thing is to not panic and remember that you can come here for advice. You do want to use the search function, though, to see if someone else has experienced the same problem.