I absolutely loved this episode, couldn't stop laughing for a second. The only negative criticism I can give it is the fact that the identity of the assassin was obvious right from the start, but as you said that wasn't what the plot was really about but more a reason for why the three where on a mission in the first place.
For not-ISIS' name though, I think the show is going to wait for some time (maybe the mid-season, maybe the end of the season) to give it one, but personally I'm hoping that when it does come it turns out to be Osiris given the rule that fictional spy agencies seem to follow for names in the series.