Okay, this is just the way I think this episode to go. At least, the way I hope it does:
I think Sam will have a crush on someone so she tells Carly she likes a guy (not getting specific) and asks Carly to give her a makeover. Carly, the ever helpful friend that she is, will happily agree and Sam will show up at school looking girly. Meanwhile when it comes time to do iCarly things get weird with Sam being different, and the ratings will drop cause the viewers liked "the old Sam." This guy that she likes (we never really see who he is) remains oblivious to her and she becomes depressed. Freddie will come to comfort her (Carly wouldn't, because she'd be happy with a nicer more mature Sam, and not notice she's upset) and tell Sam something along the lines of, "Don't ever change for a guy, Sam." Then as he leaves he'll say something like, "Besides, I like you just the way you are." The next day and next iCarly Sam is back to normal and so are the ratings.