I honestly wouldn't drive it.. if it is something that's fixing to let loose, finding an engine shop that could rebuild what you have might be cheaper than buying a entire new block.. but, I haven't priced either thankfully!
Welcome, hopefully your "knocking" issue is nothing catastrophic. That's proven to be costly out of warranty as @Brady mentioned.
When are you expecting to hear back from the dealer?
Welcome!
Some dealers have great diesel mechanics, others not so much. Hopefully they will find your issue. I'm assuming you're not pulling anything when it's overheating?
I was going to say, would it go down far enough to get the oil out? I used one for my Seadoo years ago because it was such a pain to change! But yes, a nice set of ramps make it a lot easier as you can get more clearance to get under the truck.
Also, I would recommend something like a Ez Drain...