How does one change the battery in the infrared key/remote for the 1999 and
newer Mercedes?  I cannot see how to disassemble the key.  I am guessing
their must be a battery in there.  Surely you don't have to buy a whole new
remote (that was something like $130 when we bought the car!).  Just curious
as the car is over five years old now and the batteries can't last forever.
The distance from the car that the remote will work has been shrinking.  I
was wondering if the battery is getting weak.  It could also be due to the
red lens at the tip of the key getting scratched up.  There really is no way
of keeping that protected in daily use. Not sure if I want to attempt to
buff that out.

Thanks in advance,
Doug