Product review (5 stars): Resurrect your dead dishwasher
Complete kit to replace dead thermal cut-off (TCO) switch.  Comes as pictured, with instructions (I've scanned the instructions and uploaded picture -- see 'customer images').  Note: follow the instructions, you will not only be replacing the old dead TCO, but cutting the existing wiring harness and using the new one.  I can't comment on exactly why this is necessary, but techs have reported that not doing this will often result in the TCO blowing again.  Process is simple and straightforward, and documented in the instructions.

This TCO fits many dishwashers from different manufacturer labels (most are rebadged Whirlpool OEM).

A failed TCO will result in your DW being completely dead -- no lights, no control panel response, nothing.  If you have lights, but the DW is otherwise non-functional, it is more than likely NOT the TCO.  Testing a TCO is simple: remove and test w/ ohmmeter.  If it tests with a few ohms or less, is good, if reads open (infinite or -1 ohms), it is bad.

Total time to replace (includes remove and replace panels, etc.) was approx. 20 mins.  Make sure you unplug your unit prior to starting work.