Yes Opportunist creates a situation where it would seem to matter if the card replacement order matters, but if you follow the order of events to its logical conclusion even if you replaced the bought card first and opportunist bought it, the original card that was bought first... would be resolved first.
In regards to the many rules questions regarding KOT I can only offer this link,
http://boardgamegeek.com/filepage/91030/quick-reference-guid...
written by a very awesome and knowledgeable gamer.
In regards to the many rules questions regarding KOT I can only offer this link,
http://boardgamegeek.com/filepage/91030/quick-reference-guid...
written by a very awesome and knowledgeable gamer.