Photo editing: Background replaced / person added to photo

"Guess who I saw at the beach last week!! Hugh Jackman!! Believe it! And to think I couldn't even take a picture... regret :-( regret :-( regret. But now to make the best of the situation — here's a picture of me at the beach earlier this year, and a random photo of (suitably attired :-) Hunk Hugh... Would you put us together in the same picture please. And make it look really really natural, as though it were a real shot. Thanks!"