I'm going to 2nd BillGrissom and encourage you to get on with renovating that engine. I did 2 of them back in the 80's, a 78 300D NA and some years later an 81 300SD. I had prior experience on Ford, Chevy, Chrysler gas engines plus 1 BMW 4 cylinder engine and I had an old Haynes manual with info for the 617 NA engine.

On the 300D, I was fortunate to work with a local machist in Kingston, WA. He had never done a diesel but wanted to try one. I removed, disassembled, re-assembled and
re-installed the engine. It fired right off 1st try, ran trouble free for years thereafter.

The turbodiesel engine wasn't covered by my Haynes, but was similar enough that I got it apart and back together correctly again with help of a local machine shop ("Thumpers") in Olympia, WA. Again, engine fired right off 1st try with no problems, despite my yellow lab puppy retrieving engine parts off my bench and dropping them into my hand throughout the process!

I re-used all the original pistons on the 300D, and 3 of the originals on the 300SD, with 2 used pistons from Potomac German Auto. Back then they charged me for 2 used pistons, but sent 5 good ones so I could choose the best.

Just take your time and think through everything as you go. You can do it. Don