[Mr.ac]

Cam plate is usually where it leaks from. But thats super obvious to check if it's leaking or not.

As for the a head gasket, it will smoke white if coolant is leaking. It will smoke black if it's leaking oil.

As for burning rubber that's usually something exhaust related. Either a rubber bushing or a heat shield that is too close to the pipe.

I would get a second opinion on your mechanics buddy. If he recommends a head gasket repair with out it showing related symptoms, he seems odd.