block heater quit begining of the week.wondering if anyone has experience trouble shooting and if you can get these parts at cummins dealer or aftermarket.

 

Try these directions from Riki's site:
Block Heater Replacement Instructions

 

First thing to check is your extension cord and it's supply, could be a GFI or breaker has tripped.
Most often the problem is just a broken wire right behind the heater's AC plug, cut it off and replace the plug after checking with a ohm meter.