nostr:npub1zdp33shl69xr0uq3x8n5gsjykq9upycwh6nqm02c3f6x0frrn0dq42vqv8 

Where on this diagram are the threads ruined & what material are they?

And no, you are not nuts; plumbers are expensive and this work is usually less complex than drywall or electrical.

https://files.sfba.social/media_attachments/files/111/066/742/119/412/859/original/688eafae277d6468.png