You would tell an HVAC guy to call an electrician rather than figure out how to change his service, so follow your own advice... *grins!*
The HVAC guy will pressure test the system, evaluate it, and tell you just about anything you want or need to know about it. The system has been working for years, so it isn't necessarily a bad one...
While I've got you here, we could always use a LICENSED electrician on the board here to answer questions. I take a stab at it every so often, but I'm sure I don't get it right all the time. Take a look at the ceiling fan question yesterday, and you'll see what I mean.
Feel free to join in and answer questions any time. Your expertise is always appreciated!