The key thought in your question is not that it's an electrician but that he "does not regularly do this kind of work".

If this is the exhaust for the cooking area, I'd say No. There are commercial/restaurant HVAC companies who do that kind of thing.

The exhaust fan is nothing more than a glorified housing with a motor driven fan assembly inside. No problem for a qualified electrician, it's not rocket science.

@Elmer J Fudd is correct, @HU-867564120 is not.

If not replaced/installed properly the exhaust fan will not acheive the necessary airflow for the restaurant, will be louder than necessary, will create structural vibration and potentially result in leaks in the roof.

We spec'd inline duct blowers for some of the bath exhausts in our new house. The HVAC contractor incorrectly mounted thee of them directly to structural members and all three caused harmonic vibration noise. They had to cut out sheetrock to correctly remount all three of them using straps or isolation dampers.