How do you find a glass guy that knows how to replace the glass on these cars? Most of the glass guyus I call will cut the glass and install the hardware around it, but will not install it into the car.
I think at that point you would need your mechanic to install it - I had to have a mechanic replace the power window motor in my 82 Trans Am (a very long time ago) because of the high tension spring that helps raise the window.
You might need a mechanic to remove it first before the glass guy can install it in the frame - I had removed the motor myself to rebuild it and sprung the spring - he told me I was lucky it didn't catch my hand in the door or it could have taken off some fingers.