heres what I would do. will cost you nothing compared to the time and $ to replace then motor and as you sit right now you cant really do any more damage to it.
let the diesel soak until the motor will begin to turn again. maybe it never does, but maybe it does. lets pretend like it does free up, clean as much sludge out of the top of the motor as you can and now drain the old oil out and turn on the car with a 50/50 mix of atf in it (in place of 5w30), don't rev it at all, just let it run until it warms up then drain the oil/atf. Now do that until the filters stop coming out full of sludge and you stop getting sludge buildup coming out of the drain plug hole. then replace with 5w30 only and you should be good to go. The biggest thing is you need the oil to get hot so it starts to clean the sludge out of there.
I've taken a 99' Silverado with 500k km on it with low oil pressure back to where it should be just by adding a liter of atf with a fresh oil change and letting it run for about an hour. He drove 5000km with the atf in it then we drained the oil and replaced with all 10w30 and he hasn't had a problem, was talking to him a month ago and his truck now has 580k km on it.
2009 Ford Escape Limited - 3.0L, 6 speed auto, 4x4, 25/33 city/hwy imp mpg.
2017 F150 XLT-XTR - 5.0L, 4x4, 3.55's, E-locker, xtr chrome package, fx4 off-road package.
20/25 imp mpg