You don't seem to understand how hot water leaves the tank and into your pipes. It is the cold water entering the tank at the bottom of the tank through the dip tube that forces the hot water out the top of the tank. So, you're plan won't work. Either drain into the sewer or if your tank is not in a basement, just use a garden hose to drain it outside. 88 gallons of water will quickly soak into the soil. You will need to open a hot water faucet in the house to allow air into the tank so it will drain. Be very sure there is no power to the heater. Changing elements without test them is folly. Your tank may be filled up with sediment or the thermostat may be faulty. In fact, I would suspect the thermostat as the first probable cause. There is a very good axiom in the electronics business. "Test, Don't Guess". Unless you have the test equipment and know how to use it, you are likely to spend a lot of money needlessly which will quickly use up any savings realized by DIY. I'm not going to predict "sudden death", but you could cause a short that could really toast the electrical components in the heater. Sometimes the best DIY advice is to call a pro when there are technical aspects that you understand.