How to Replace parts in a RTL300TQ?

I have a RTNL300TQ gas log heater. It is uses LP so I believe that is the model # (the other model # on the manual is RTN300TQ). We can get teh pilot light lit but when we turn it on it will go out after about 10 seconds. We cleaned the thermocoupler, but still have the problem. We were thinking that the thermocoupler may need to be replaced BUT we cannot figure out how to take this apart to even get to the thermocoupler. Does anyone know?