Gary, it depends on what you have. My unit was a Seaward, and any change many some easy cuts in the counter top. Unlike many, I was left with a gap regardless of replacement unit I picked. That's why you'll see the border piece of stainless on the counter. It matches the unit, so most wouldn't even notice it.

Some factory installed units were 120V while, while others were 240V. As long as the current wiring is of the correct gauge, and it should be, you're good to go. If the one you have is 120V, you can use the same wire, just put domes red tape on the wire wire and take it off the neural bus and move it to the circuit breaker. A 240V breaker has 2 power connections instead of 1 that is found on 120V breakers. You may have to move breakers given a 240V breaker has to straddle a line 1 and line 2 connection tab. Okay, if your current unit is 120V, the circuit breaker change may be more than some want to tackle.

Check your current breaker our the unit and see if it's 120V.

And yes, we had to change our cookware.