Arghhhh.... I totally got on my soapbox with my husband after reading your post. Sometimes I wonder what these LBS guys are thinking. You're a new rider and not a 20something. You're not a racer - neither am I. You probably want to still be riding 20 years from now. What would happen to your knees if you kept trying to push a big gear? What a great way to turn someone off riding. Kudos to you for looking for ways to make it work.

I ride a 46-36-24 in the front with a 12 - 28 rear cassette. You don't need to have huge gearing to go fast. I do a lot of hills and spin up them in the easy gears, but with this gearing I can still do 25 on a flat road.
Here's a link to where you can so some more reading.

V.
Peter White Cycles