Keyless entry system

Hi, I have a 2006 Merc Grand Marquis which I actually bought yesterday. The car did not come with a manual and the dealer (not Merc) does not know the keyless entry number. I looked in the usual places and couldn't find the number. Then I checked the module under the seat and sure enough there is a 5 digit number there. Punch the number in and nothing happens except the headlights come on. Is it possible this isn't the correct number? I called the Merc dealer and when they found out I didn't get the car from them, they didn't seem to interested in helping me (but for $44.00 they could put the car on their machine and get me the code). All I want is to be able to use the keyless entry. Anybody have any thougths, ideas?

Oh, one other thing, where would be the best palce to get an owners manual? Again, the Merc dealer doesn't seem interested in helping me.

Thanks, Mike