That's one way to get the code but if you bought the vehicle from them and they want to charge you $100 that's almost a crime. I work in a Ford dealership and it takes about 3 minutes to go in and retrieve the keyless entry code. Look in the glove box or inside the owner's manual for a small credit card sized card that has the keyless code on it although it's often missing in used cars. I do it all the time at work and like I said it literally takes just a couple of minutes to retrieve the keyless code.