Hi SixZeroFour,
you will find the flame check system a real pain. Sooner or later they fail, and there are no parts available from Weber.
Front burner has to be on ALL the time for ANY of the other burners to be lit.
While you have it apart just remove it, no need for a new manifold.From memory it goes somthing like gasline to thermocouple to manifold.
Just remove the thermocouple valve, connect the gasline direct to the manifold as with any other 1000-5500, and leave the plastic round button in the control panel hole for looks.
It is fun to restore the 'Top of the Range' gassers. Why settle for less?