my key will not open my car using the button and if I put key in the lock and get in the alarm goes off. Just need to know what sort of amount I am going to be paying out.
In the uk??

It can't be done. The chip in the remote is a PROM that can only be burned once.
If the remote worked in the past there is some other problem with the car.

My Local Key Cutting Place Have Told Me That Mercedes Would Have Made Up 5 Or So Keys For Your Individual Car Incase Of Problems Like This. Get In Touch With Meredes And Ask Them If They Can Send You A Replacement Key. In The Mean Time, When You Unlock Your Car Using The Key In The Door And The Alarm Goes Off, Use The Little Red Dongle Thing On Your Keyring And Put It In The Slot Inside The Glove Box On The Left Hand Side. (This Deactivates The Alarm, Instead Of Putting The Key In The Ignition.)

Hope This Helps!

Cheers, Tom.