Being about your age and doing most of my riding in Southwest Travis County, I can appreciate your problem. There are several different ways to go, but on a bike similar to yours, I found the best fix was a compact crank. You should be able to keep everything else if you go this way.
http://www.jensonusa.com/store/produ...+Crankset.aspx
If you want to go a little more vintage in appearance, you can go this way:
http://www.jensonusa.com/store/produ...t.aspx?sc=FRGL