I agree with
@jssailem up to a point. I would not attempt a job like this without compelling evidence that it was necessary.
I have over 3100 hours on my 1997 Volvo MD22L-B and I change the oil and every fall, probably just like you do. I change the oil when it is hot and I have never observed any "gunk or lumps" of stuff. This change each year is at about 150 hours of run time.
Now I do pump the oil out through a tube that goes to the bottom of the crankcase, but the flow speed is low, so there could be some residue in the bottom somewhere.
If I were really concerned, perhaps a quick flush with an engine cleaner additive, then drain and change the filter and refill with new diesel oil would be my cleaning attempt. I have never done this, so I would research diesel engine cleaning before cleaning.
You do use detergent diesel engine oil, don't you?
Why don't you talk to a diesel rebuild shop and get a better real-life experienced opinion?
As always, YMMV.