You shouldn't need to. [See my answer to your question: "Why won't my oven stay lit".] If by the thermocouple you mean the Flame Safety Device (FSD of FFD), that needs only to be replaced if the oven lights but does not fully 'flame up'. It is easy to replace (I've done one and I'm not a gas fitter) if you have the right spanners and screwdrivers.
ROO from Pompey, February 2009
