I have no trouble with wooden molds in the oven, as I CPOP frequently. Pre-warming in the oven is fine. As a precaution, just pre-heat the oven, then put the wooden mold on top of an oven-safe tray of some kind with a towel or parchment paper or a towel to protect the tray from anything on the wood (old soap, glue, etc.). Before you put the mold into the oven, TURN IT OFF, then put the mold in the pre-heated oven.
I emphasize turning off the oven as a precaution to make sure to develop a habit that will prevent you from accidentally forgetting about it and cooking your mold for some extended period of time. It's too easy to get distracted and forget about it. Why take that risk?