[Drachenfire]

My house was built in '73 and the original dishwasher was hard wired (and hard piped 🤬).

The replacement dishwasher came with a plug so using the existing hard wire and an Old Work electrical box, I just installed an outlet under the sink. Aside from the cramped space (I am not a small person), it was not difficult at all.

NOTE: Ensure the power to that wire is turned off. If you are not sure which breaker feeds it, shut off the power to the whole house. Even then, still verify with a tester

 

[Drachenfire]

Is installing an electrical box and a switch to operate it under the sink an easy DIY? I thought an electrician would be needed to stay within code, so I didn't think about installing one. And I am unsure if the switch can be under the sink or has to be on top of the counter.

An outlet for the dishwasher does not require a switch.

However, NEC requires a GFCI outlet for plug in dishwashers with a a few exceptions. However, while a little more expensive that a standard outlet, a GFCI is cheap insurance against electrical shocks in the event of a water leak.

This video might help. Although the person in not using a GFCI, the process is similar. Just read the instructions that come with the outlet to ensure you wire it correctly.