I just bought a 240d with an air cleaner mount nut in the engine. (Price was appropriate for the issue.)

The PO dropped it in the intake and now the engine has a bit of a knock. I'm not exceptionally worried about saving the engine but think it's worth trying. The car is a manual transmission which is what I really want for my 300d turbo, and if I can't fix this one I'll pull the engine and transmission, transmission into the 300 and maybe down the road throw a largeish cheap gas engine in the 240 as a sleeper.

First thing though I want to see if I can save the 240. Does anyone have any good trick/suggestions for getting it out of the cylinder? I'm planning on pulling the intake and glow plugs and seeing what I can see.

I did a search and the only similar post I found suggested pulling the pre combustion chambers.

Question 1-
How long does it take to R and R a head or the pre combustion chambers? Anything special I should know?

Question 2-
Is it more likely that the engine is done (bent rod or smashed bearing)? The PO drove it a couple blocks like this, so I ran it for 30 seconds to get it on the tow dolly. Seemed to have smooth power (for what it is). Part of me just wants to drive it as a test of how tough these motors really are, but I know that's a bad idea.