Welcome to the forum!
This is a difficult one. It would likely benefit you to find out just what it is that was blocked off, and check a vacuum diagram for the proper routing of all the other lines.
As for the fear of working on a diesel, don't worry about it! The old benz diesels are as easy if not easier than you vw's and audis to work on.
Now to your smoking problem: Is the car buring motor oil? It sounds as though some fuel is getting in when it shouldn't, or possibly oil. Let's hope that it is not the latter, but a compression check might do you some good. Also check the valve seals.
If it is fuel, then you might have a fouled or faulty injector. Try running some Lubro-Moly Diesel purge through the system (directly, not in the tank) and see if you benefit from that before trying anything else.
It is difficult to say if the mechanic saw something needing to be replaced while he was in there, but there are a number of things that can be serviced on the IP while you are in there including delivery valve seals and the fuel shutoff. I don't really recommend replacement of these until they fail.
\'87 Mer-B 300D (220,000 miles) (sold)
\'93 Mer-B 300D (173,000 miles) (sold)
\'87 Porsche 928 (101,000 miles)
\'98 Dodge Ram quad-cab (250,000 miles)
\'2001 CLK430 Cabrio (50,000 miles)
Past cars: 1969 mercedes 250, 1981 300D, 1972 220D