HOUSTON (Reuters) -Exxon Mobil want to "participate" in Hess Corp.'s sale of its Guyana oil production assets, and extract value from the work it has put into developing the country's offshore fields, two of its top executives said on Wednesday. A three-person panel in May is to decide whether Hess's deal to sell itself to Chevron can go ahead on its original terms. A challenge by Exxon and CNOOC Ltd has stalled the second-largest deal in a recent wave of oil megamergers.