[CQ-Contest] CM500 Headset mic element replacement

[Dave Hachadorian]

The microphone in my Yamaha CM500 Headset has failed.  DC 
measurements at the plug show:
tip and ring shorted
1270 ohms tip to shell with negative ohmmeter lead on shell
810 ohms tip to shell with positive ohmmeter lead on shell

The above measurements lead me to believe that the problem is not 
at the connector end, but rather in the element. I'd like to take 
a crack at repairing the unit.  Mouser has a wide selection of 
electret elements, starting at $0.58.

Any ideas as to how would I go about disassembling the mic 
enclosure, and can someone recommend a specific electret element?

Thanks in advance.

Dave Hachadorian, K6LL
Yuma, AZ