Oil thinning isn't an injector problem, but the HP pump front seal leaking. It is driven from the first timing chain, and anything leaking from the front seal will end up in the sump.
Important to get it sorted sooner rather than later if the sump is filling with diesel because there is a risk that the engine can run away with carryover of oil.
Unfortunately it sounds like a too long bolt has been used to secure your engine cover, and it has broken through the cam cover.
Not a problem as long as you keep the bolt in place.
There are other bits of diagnostic kit that can read fault codes and more on the pre OBDII diesel cars, although T4 is by far the best.
You can knock up an injector leakback tester cheaply and easy enough, so worth checking the injectors before going down the electronic diagnostic route. This is my GhettoTech version:
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