locating keyless module

Recently purchased 2000 century w/o remotes (orginally an avis rental car is what the dealership told me when I went in to price the missing cup holder that goes in the consule - in case someone has one) where can I look to see if it has the keyless module (what does it look like). Also if it wasn't equipped with one - what range make/model of cars that fit so I can get one from the (junk yard) that will plug and play. I will check for remotes on ebay unless someone has some - then use the programming instructions I saw for an 99 century. need help - thanks