While I worked at a restoration shop I helped with some glass installs. Generally if the procedure involves some sealing or caulking compound we used the modern version which is black urethane glue/sealer. The stuff works really well. However it was no fun at all to work with and if it got on anything it was pretty much there to stay.
So in many occasions we had a professional glass service install them.

If the price quoted sounds reasonable I'd let the professionals do it as they're more practiced in using that nasty sticky urethane.

If you don't have a nice paint job and or don't need it to be just right perfect may as well do it yourself, or if the price seems unreasonable. It's certainly possible to do it yourself/with help and learn as you go.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-