A: What you’re asking about is essentially: which happens first, the completion of seven panels of gold via the Silver Dragon, or the exchange of the Goal cards?
The answer is that those things happen simultaneously, so after executing all of the results from the Action card, you see who’s meeting the win conditions. So it’s the person who ends up with the yellow Goal. If you traded to get it, that’s you. This a common winning strategy ploy.
The same question applies to similar moves with the Rotate Goals action (blue) where someone uses Rotate Goals to gain the blue dragon Goal while simultaneously changing the Silver Dragon to blue for the win.