Ben,

I regret so much you play so stupid, because I know you're not.

The mistake is asking a customer without knowledge of the matter if they need to repair an END OF LIFE part.
This is not ethical behaviour, but plain money grabbing and profiting from the ignorance of a customer.
You don't do that if you want to build up a long term relationship with a customer.

"Repairing" the print head that is past it's END OF LIFE is the responsibility CEL bears and caused all the problems that came after it.
Since CEL does not have spare print heads any more, it becomes clear support in this case choose the option where they can make money the fastest way.
The correct would be: customer, sorry for your print head, but we advice to wait until we have new print heads in stock and buy a new one.

That would have been not so fun news, but perfectly acceptable and honest.
I would still be without a working printer now, but would not have followed the ill advised actions by support that led only to further problems,
problems that started because I got an print head back to work with that was END OF LIFE, and that support failed to see the symptoms (or look for it) of a blown seal.
So in the end mistake was piled upon mistake.

You simply can't defend that without damaging your credibility as an independent contractor.
But I perfectly understand that you prefer not to bite the hand that feeds you,
after all as a private contractor working for CEL you must have a considerable income out of it,
certainly as we all observe in the CEL forum the huge amount of work you spend in playing a huge wall between us and CEL staf.

To be blunt, in half of the cases you give very FAST and good response on the forum, although from time to time you are to mechanical and fail to see when software is a part of the problem.
In the other half of the cases, you're simply in the way between us and CEL, because in a lot of cases we want explicitly CEL to answer, not you, because as you say,
you are not there (at CEL HQ), but are "just" an external contractor.

To sum things up and stay at topic:
support made blunder after blunder in this case, and CEL needs to take responsibility.
That means repairing potential damage done by following the instructions from support,
and pay back the ill advised repair of the print head.