Just cahnged the oil on my 94 eldorado and the indicator reads o%. Do i have to reset this, and if so how do i reset it?

Yes, it has to be reset manually when the oil is changed.

Check http://caddyinfo.netgetgoing.com/oillifeindicator.htm for a complete list, but for your 94 Eldo:

All Models ex. Fleet-wood 1994-97
Press the "INFORMATION" button until "OIL LIFE LEFT" is displayed. Press the "RESET" button until "100" or "0.0 OIL LIFE LEFT" is displayed.

Bruce is correct.
When you push and hold the reset button 3 X's will show up wait until those go away and it reads 100%

thanks, that did it.