The hob plate is usually part of the main chassis so it's a major stripdown to remove it . Usually the thermocouple is replaced by removing the side plates As Dustydog says working on the oven comes under the Gas safety ( installation and use) Regulations 1998 and does require an trained ,certified ( not certifiable) engineer ( but not necessary a gas safe one for mobile caravans) to work on Gas appliances, even pulling the oven forward may induce a gas leak in the gas connections and the gas system would need fully testing after refitting.