key fob on 2005 Expy has quit working

My key fox on my 2005 Expedition EB has quit working. I would try the other key fob / key but my wife lost it.
Does anyone know how to get the key fob working again ?
Does anyone know how much a replacement key and fob cost ? Do I have to go to the dealer ?
Thanks, Lynn
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Some parts stores have a little test receiver at the counter to check it. It also has a "coin" type battery in it similar to or identical to most computers that must be replaced occasionally. They test it and sell you a new one if required. If it is dead, you can get another key fob off eBay and program it for your vehicle with the instructions provided. They are much cheaper on eBay than at any dealer. I would test for a dead battery first.
Lugnut
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