If Butler installed a BOP neoprene seal, it will not be that easy to remove. If Yellowtail can get all the old seal removed, then they can go back to the rope style seal without removing the engine as you described.
It's too bad they don't make the old style rope seal like they used to. You probably have the old style with asbestos in it. They had a pretty long service life. The new rope seals are manufactured differently and don't seem to have the life expectancy.
