Timing is of the essence: Our 1988 Mercedes-Benz 420sel throws a sucker punch

A few on the locals 'round here

Freshly redone seat, with a donated 500SEC lower half courtesy of Jim's parts room

A chunk of timing guide, it's clearly been around

A painful view of the valve cover

Shiny valve relief

A clean shop makes for a stress free space
​All was going well on the W126 forefront in the Workshop until I decided to pull out Frank and clean up the floors. As usual, the V8 roared to life and casually pulled out into the space beside my Workshop. Leaving room for me to clean up the oil dry from all the various fluids that had found their way out of the engine during the revival work. A few dust clouds later, the shop floor was clean and ready to house its four wheeled tenants again. 
Not so fast!
I slide into my freshly 'redone' drivers seat, expecting Frank to come back to life, and to my surprise, it spins over then suddenly stops. "Well that's weird" I thought. After a few cranking attempts I noticed the starter was pluming smoke, so I decided I should probably  the battery just in case. Confused, and betrayed, I fired up my John Deere and yanked Frank back into the workshop. In complete disbelief, I let Frank sit for a couple days.
All it takes is time
It was a cold morning in the shop, and things were froze up outside, and little did I know, inside too. Gathering my thoughts, the most logical starting point is to see if I can spin the engine over by hand. Four ten millimeter bolts later and the fan is off the engine. I grab my 27 millimeter socket and half inch drive ratchet for the moment of truth. After many attempts of moving the engine back and forth a few degrees, there is a dead stop in both directions. Time to rip off the valve covers. The passenger side shows nothing out of the ordinary, maybe there's hope? The driver side was a different story. There was a deep gouge in the valve cover itself from the timing chain, and both timing guides were broken. I grabbed my inspection cam and noticed there was a chunk of the timing guide wedged between the chain and timing cover. After some fighting, I was able to pull it out, but that was not the source of our 'sticking point'. Proceeding to look down the spark plug holes, I found that cylinder three could have contacted a valve. Valve contact at low engine speed doesn't necessarily explain the engine being stuck. As if the engine fighting me wasn't enough, I went to hook the battery up to roll the driver window down, and I heard a little motor whirring. Unfamiliar with all the electronic gizmos on the W126 chassis, I assume it's just something under the hood. As soon as I heard the familiar "thunk" of the door locks, I knew I was in trouble. Lets just say a coat-hanger, an airbag, and three hours later, I was back into the car.
What's next?
There are a few ways to proceed from here, with one way being more grim than the other. We took this $700 car from a neglected non-runner to a shiny, running and driving machine. The more unfortunate fate for Frank would be a future in "The Pen". Neither Jim and I want to do that to such a nice car, so we've decided to see if we can get it back up and going. We have a parts 420SEL with the same engine but with less miles. I noted down when we got the parts car that the Camshafts were no good. Since it is lower miles, maybe the Cylinder heads themselves would be good and we could swap the nice cams from Frank.  Is it worth getting a timing chain, guides and a head gasket set? Time to pull the engine and see what survived.