I am TRYING to replace the engine wiring harness on my 1995 C280. I started at the end on the passenger (right) side, have done the engine top, and am moving on to the engine front and toward the final connector on the driver's side in front of the wheelwell. That last connector on the harness is a long multipin device and I can not see how to remove it. I did discover what I believe is a slide-out lock at its base in the rear, but with it slid out the plug is still in there tight. It has to be lifted from the rear, where the wires enter, in order to come out, but I am afraid there is still something holding it. Can someone give me guidance here?

Also, on the same final connector, my new harness has one bundle of wires entering the housing while the old harness appears to have two bundles of wires going into the connector. Since I can't get it out, I can't see what the situation is on that. Both harnesses have the same part number. Any ideas?

And another thing, I cracked the housing of something trying to get another connector off. It is located on the head at the front of the driver's side (left) camshaft housing, is attached by two allen key bolts, and my guess is that it may be the tach sensor. Can someone indentify this for me?

Any help is appreciated. Thanks.