You're right as regards 18,32 - but it is still a proper word that is being replaced by another word. The resulting word is not a proper word. I've finished it now, and submitted it, so I'm pretty sure I've got the right words, - it all fits.
A very enjoyable Genius after an excellent Prize xword from the now 90 Araucaria - has highlighted for me the blandness of the AZED sandwiched between them!