We would appreciate advice on how to deal with a problem with a gas leak from an injector.
The engine is a Volvo 2003T with 2500 hours on it. Injectors were replaced with overhauled ones about 800 hours ago.

When starting from cold, there has been a “ticking” noise like a loose tappet for over 100 hours of use. This noise diminishes substantially when the engine is hot. Of course I checked the tappet clearances. All are OK without even requiring adjustment.

Today, the noise was worse, and I noticed a slight puff of smoke from the injector. The puff is also detectable by a hand held close to the source. Close inspection revealed a visible, but tiny, oozing leak up the side of the injector, from inside the cylinder head. It is much less once the engine is warm.
Engine runs OK but does not start “first bang” like it did a few hundred hours ago.

Inspecting the valve cover beside the injector, and the fuel piping suggests that the gas leak is not new, but we cannot guess whether it has been for 50 hours or 500 hours of engine run time.

The injector seems to rely on a close clearance fitting into a copper sleeve in the cylinder head to seal. Looking at our spare injector, we cannot see any shoulder to seal against.
Obviously we should pull the injector and look at it. We tried, but cannot move it, although we have take all 3 injectors out before without difficulty. I suspect the sleeve/injector surface is corroded by the escaping gas.

We are in Norway, en route from an anchorage in an uninhabited fjord to Bodo, where there is a Volvo repair shop. I want to be prepared to talk with him. At this stage I have no way of knowing whether he is the “We must overhaul immediately” type or not.

I suspect we need to replace the copper sleeve in the cylinder head that holds the injector. This requires removing the head and special Volvo tools. (Expensive, especially in Norway) Once the head is in the shop, of course valves should be reground etc.

Questions

If we find that the Volvo shop cannot do the work within a reasonable schedule (or has time only for a quickie, temporary repair) how many hours can we reasonably run the engine?.
Will we do any damage beyond the copper sleeve and the injector?
What is the danger of complete engine failure?
I appreciate that you cannot see the engine, but comments from those with experience would be appreciated.