Well that sucks. But…clean breaks. You can drill those out and extract them. Clean the threads and put in new bolts. Center punch then start with the smallest drill bit in the set. Go slow and steady light pressure. Drilling oil is best but you can use about any oil to help keep the bit from getting hot. I use penetrating oil as that’s usually what’s handy. Drill all the way through. Then go step by step in drill bits until you can fit an extractor. Usually the heat of drill will help break out the rust. Worst case scenario, you drill out the hole, ruin the threads, find a bolt, nut, and lock washer and install through that hole.

Yes or at the very least clean it, clean the terminals and add some sort of protectant. But leaking battery can lead to cable issues.

The coil is glow plug related. Cel and your DPF filter are the other two. Likely you have a bad glow plug or similar that’s not allowing it to regen. Hence the cel and DPF. You’ll have to pull codes

And that’s why you don’t handle it by the shaft!

It’s not even really the weight. It’s more of how awkward it is to hold. Two guys can handle it easily. I can say I’ve lifted a ranger transmission by my self but I’m 6 ft 300lbs. Not above my head but up off a trans jack and a new one back up. Roughly similar for size.

Get a second opinion. But it’s entirely possible that a chain is in your future. That’s an interference engine, I don’t know about catastrophic failure but it’s entirely possible that aluminum engine could damage everything if you smash a valve into the piston. 8k sounds like a lot for a 4 cylinder motor tho. 8k would cover another motor.

It’s a lot of work to get to those injectors. I’d have them do all four, it should be the same labor. Pricing it’s not too bad otherwise