2020 Cascadia dd15 18sp manual questions

I'm looking at a Cascadia, mid roof, 505hp, dd15, it has 877,000 kms or 544,000 miles. I like the truck, its from a mid size fleet, mostly deck work. Runs great, I'm going to do an oil sample and maybe a dyno with blow by if they will let me bring it down here.
Questions are;
What should I be looking for?
How real Are the oil pump issues?
If I do it, what is the best software I can get?
I don't regional now, no more than 4-5 hrs from home and my shop. "Modifying" it isn't out of the question if it became a problem child.

 

I had a 2010 i bought brand new, had it one year, affectionately called it the "Crapcadia" it was horrible. I have e 2012 columbia glider kit but its getting ling in the tooth like me and I'd like to have my last 3 years in something a little more comfortable and quiet.