Fairly simple job. Hook a garden hose at the bottom and drain it. Turn off power to it, disconnect wiring and hookups. Will need help to remove old one and replace it, they're not real heavy, just hard to get a hold of.
One thing to remember, DO NOT turn the breaker back on until the tank has filled up and you have water from all faucets. You will burn out the heating elements, I know this from experience.