car clicker replacement

[Maejewell]

I am in need of some advice on what to do about my key. So I have a mercedes S500 2002 and I have the regular mercedes key fob with the three buttons for unlock, lock and trunk. The key fob was on my key chain and somehow the key fob shell came off and is now lost but i still have the actual thats inside of the remote, not sure what its called. It works to unlock the car and everything, and I wanted to see what I had to do next to get a working key, and if having the key still helps?