Remove the burner from the TRH (details)

Use a standard flathead screwdriver to loosen the 4-front plate screws and remove the front plate & flame/air tube assembly.

Disconnect the ignition transformer lead wire by gently grasping it with your fingers and pulling it straight out.  A slight side-to-side motion may help.  It is generally a large RED wire.

Remove the ignition Transformer Retaining screw

Remove the ignition Transformer