CLK Avantgarde Auto Gearbox Problem

[Green Halo]

Hi All. I have just started having a problem with my 2000 CLK. When I start the engine and select drive the uptake is a severe clunk and the car gets stuck in gear. Nothing is displayed on the dash and the gear indicator is blank. With the engine ticking over I can only select neutral or drive. When I switch the engine off I can push the gear lever into neutral reverse or park. Restarting the car and the problem has vanished.
The car has done just under 80,000 but the gearbox is a replacement box at about 58,000 miles by the owner before last.
Searching this forum suggests that engine mounts or electrical plate might be the cause of the problem. Is the electrical plate a DIY job or best to go to a professional.
Any thoughts or suggestions are welcomed.
Thanks

 

[Green Halo]

I should add the car spends a fair amount of time parked up on the kerb outside my house. Probably goes four or five days without use.

 

[sync vr]

have same problem with my clk but mines a w209 2005 my best friend is mercedes specialist and is going to fix it for me but he said its either gearbox ecu as oil can run down wires into unit or gear selector is faulty quite a common problem