I don’t see how they’ll let you use a TM to get Surf as it would defeat the rarity of the Pikachu. It’s like the Christmas Pikachu with Quick Move “Present”. Sure you can use a TM to change it but you can’t get “Present” again if you do. The “park” part of the deal is only if you want the rare Pikachu but the other goodies from the event applies everywhere–i.e. doesn’t matter where you are. Someone told me the game registers a “park” where the map shows a dark green color. I’m not sure if that is true. Also, there are legitimate parks the game does not register as a park … be aware of that.