Bus. & Prof. Code, § 9793

No repairperson shall commence work for compensation without specific authorization from the customer or his or her agent, in accordance with all of the following requirements:

(a) The repairperson shall give to the customer either of the following:

(1) A written estimated price for labor and parts for a specific job.

(2) A written estimate of the maximum cost for a specific job that does not differentiate between labor and parts, but which shall not be exceeded by the actual cost of the job, including labor and parts.

No work shall be done or parts supplied in excess of, or different from, the original written estimate without the separate oral or written consent of the customer. If the consent is oral, the repairperson shall make a notation on the work order and on the invoice of the date, time, name of person authorizing the additional work or change in work, and the telephone number called, if any, together with a specification of the additional parts and labor and the total additional cost.

(b) If it is necessary to disassemble a general aviation aircraft or its component in order to prepare a written estimated price for required work, the repairperson shall first give the customer a written estimated price for the disassembly and reassembly. The estimate shall also include the cost of parts and necessary labor to replace items such as gaskets and seals that are normally destroyed by disassembling the component. If the disassembling might prevent the restoration of the component to its former condition, the repairperson shall write that information on the work order containing the estimate before the work order is signed by the customer.

The repairperson shall inform the customer orally, and conspicuously in writing on the work order, of the maximum time it will take the repairperson to reassemble the aircraft or its component if the customer elects not to proceed with the work. The repairperson shall not charge the customer for more time than the specified maximum time if the customer elects not to proceed with the work.