I nicked the membrane over the home button, and I think that is the reason now why finger prints are not getting read. I...

Is the boiler actually corroded (Metal is partially dissolved due to chemical reactions), or do you have lime deposits from hard water? If the metal is corroded, then there is little you could or should do, short of replacing the boiler. One way to judge what you are dealing with is where the discoloration is - if it's mostly where the water is, and expecially where the water gets hot (at the bottom of the boiler), then it is most likely lime deposits. If the deposit is grey and more or less everywhere, then you might have chemical corrosion going on. If it's lime, then you might be able to dissolve it with a strong citric acid solution. You can find citric acid in the canning aisle of a reasonably well-stocked supermarket or hardware store. Use the stuff that people use in their preserves, Dissolve as much of it as possible in distilled water (again, supermarket), and run it through your espresso maker. After that, rinse with lots of water - a couple of runs, I'd guess. This should help, and should be...

There are two sources of sound that I can think of. The first is a whining sound as the flash powers up before you trigger it. This is a chopper circuit - the voltage from the batteries is about 6 V DC (direct current), but the flash bulb needs much higher voltages to light. It is very hard to increase DC voltage, but fairly trivial to increase voltage in an AC circuit through a transformer. In a flash a chopper circuit chops up the DC voltage by quickly turning it off and on. This creates AC voltage and current, and that can be fed into a transformer to increase the AC voltage. This secondary AC voltage is then turned back into DC voltage, which can be used to charge a capacitor that is used to store the electrical energy until; it is used by the flash bulb. To the best of my knowledge it is the chopper circuit that can be heard. It's probably the transformer that gets wiggled (physically), generating the sound. The whine is normal and nothing to worry about The second source of sound is the discharge of...