Based on your "Problem Statement" no one will be able to advise you what part to replace, more information is required.
When you say "My MX3000" has shut down totally" do you mean no standby as well ?
If the TV appears totally dead including not in standby, then the problem will most likely be:-
- The protection circuit cut in to protect the TV normally caused by over current from some part of the TV
- The power supply itself has a fault.
In either case you will need the assistance of someone who can fault find this type of problem.