Sadly I suspect you may be right. The seals may have been permanently damaged by two weeks of immersion in the wrong type of fluid. Gear oil and rubber do not mix.
In your position, I'd certainly try using diagnostics to flush the system. I'd be keeping my fingers & toes crossed, and I'll do the same for you.
If flushing the system doesn't work, there are a small number of folks out there who advertise a service to rebuild these units with new seals.
This is one such, though I've no experience of this particular seller.