Does it take about 10 hour to remove the head only or to remove and installation?

full R&R is 10 hours
 

Full Remove & Reinstall is 10 hours.

I measured the depth with tire depth gauge.

Even if I remove the exhaust manifold, I will have nothing to grab.

a = 15/ 30 inch
b= 22/30 inch

It looks like someone is going to have to drill. It may be possible to drill it on the car. I know you said there isn't enough room, but if there is room to get a right angle drill in there you might be OK.

To get a straight hole, you can make a fixture. Use a piece of flat steel about 3/8 to 3/4 thick and set it up to the exaust manifild. Just don't break any more studs taking the manifold off. It needs to cover at least the the hole where the broken stud is and one hole on each side. Drill holes for bolts to pass through the manifold holes and through the flat steel. There must be as little play as possible. the bolts must be snug in all the holes. The middle hole must be drilled carefully in the center of the hole that the broken stud was behind.

You will need a drill bushing. get one from a industrial suplly house like Kaman Bearing, or is it Kaman engineering products now? I would drill a smaller hole in the center of the broken stud. To do that, chose a drill bushing for the drill bit you are going to use. Drill a hole in the fixture you made. The diameter of that hole is determined by the outside diameter of the drill bushing. Then press it in place with a hydraulic press. In other words whack it down with a hammer. It must be straight or you are screwed. The center of the hole must match with the center of the broken stud after the fixture is in place, or you are screwed.

Then bolt the fixture in place on the head and with a drill with a right angle adapter, if you need it, carefully drill a hole into the center of the broken stud. If the bit snaps off, you are - - - well you get the picture. Then you can use a stud extractor. screw it in and if you're lucky the reduced preasure caused by drilling the hole in the middle of the stud will allow the stud to back out. If you break off the stud extractor - - - you know. You can redrill the hole until you have a hole that has taken out the body of the stud and left the threads. If you manage that, pat yourself on the back, and tell yourself you're good.

10 hours to R&R the head? At least you get a chance to evaluate the valves and install a new head gasket and timing chain. Then you can check the cylinders for wear.

How about trying to pull the manifold and sticking it back in place with no gasket and using the roofing tar? It could work. It has worked on gas engines. Do diesels run a lot hotter?

Is the "heat resistant silicone" you tried but faild a kind of muffler & exhaust sealer?
http://us.st11.yimg.com/store1.yimg....1_1893_8388600
I wonder why no one suggested putting muffler & exhaust sealer creme around the edges where exhaust manifold meet the engine. It can be done without removing manifold, turbo etc.