I don't think you need to be an expert glassmaker before you go and find out if there's a market for "glass services"(if that's what you are interested in). It's enough to go out and talk to glass owners and find out if they have a need for an expert to maintain or restore their glass and if they do, what they will pay. If they do, find an expert glass maker and hire him or her. Also your interviews might help with what kind of "expert glassmaker" you need.