1993 Programming Keyless pad

Hello everyone! I just bought my first big car. Its a Chyrstler New Yorker. So far I love it. Although the people I bought it from said their alarm would stop all activity when the wireless battery went (they only gave us one unit), and it is time for a new one. Now my wife is panicking and is afraid to go anywhere.
We called four dealers and they all want approximately $100.00 just to program one unit. Does anyone know how to program it?
Also since this is my first experience with this car, does anyone know anything I should know particularly about these cars?
Thanks!
RoboNew Yorker

most of the time that is a scam but not always u can usally just replace the battery your self providing the unit is not sealed. but if u do do it ask what type of battery it takes from dealer and go get it before taking out old battery. just going through old threads and u have probably already fixed it but anyway if u have u know for next time.