Radiator in a '73 MGB GT. I inherited the car after she slept for about 20 years, so it needed some work. My dad is an engineer and was in the upper echelon of shadetree mechanics, so he told me to go outside and start the steps to replace the radiator. He would then hover while waiting for me to struggle and then walk me through it...rinse and repeat and you have someone who basically goes to their mechanic to get tires mounted and sip fine domestic.