What's your commute like? If it's fairly flat this may be a golden opportunity to replace the wheels with single speed and go single with the old bike while beginning to look at a newer or new geared bike.

In a fit of enthusiasm from reading Sheldon's page about fixed and singles I fixed up a bike from a $14 frame and some parts left over from other bikes and various bargain purchases. Little did I know that it would turn out to be one of the sweetest road bikes in my fleet. I rode it enthusiastically for a good 6 or 7 years before being lured by a new and younger face in the form of my Redline 925 and sold it to a good and appreciative new home.

The point is that if you don't have any killer hills on your route a single speed may prove to be a great way to go with this older frame. It'll avoid a heap of the upgrade expense issues and if it clicks with you like it did with so many others of us you'll be doubly happy with the old veteran.