There is another lengthy thread currently about "how troublesome were MBs" or some such...
Your technicians logic is going to quickly make that free MB one of the most troublesome cases on the internet.
If its not broke don't f with it. So much cautious maintenance projects, indicate a lack of ability to identify the problems. The intake almost never leaks between the halves (until someone reseals them). The injector seals, idle air plumbing, and swirl chamber seals can easily be done from the top and the cost is small as the labor should not be much.
If you get ten grand in the top end of that free 420 you will have used up your freedom. Treat the rest of the car that way and in a year or two you will be telling the world how expensive MBs are.
It really doesn't do much good to built builtproof engines if you redo everything at the first failure.
Bosch Master, ASE Master, L1
33 years MB technician