The insurance company will agree on what work needs to be done and at what price. They will then reimburse you for the cost of the work accomplished. You will have to pay the cost for any additional work. Have the mechanic give you a separate bill for any work not agreed upon with your insurance company.
Know Each Party's Responsibilities
The insurance company is not responsible in any way for workmanship. The plane's aesthetics and operation are your responsibility. You are responsible for the repair. The insurance company will only reimburse you for the cost of the repair.