Strictly speaking, as Toby says, it's a statement, not a question, and therefore should not have a question mark appended.
However, if when you hear the dialogue spoken in your mind it comes with that stupid... er... annoying... er... contemporary (?Australia-originating) upward inflection which is increasingly heard at the end of perfectly ordinary statements, then yes, add a question mark to show that the character is saying it that way. But be careful. If the speaker does it once, he/she is likely to make a habit of it. (I have a niece. I know whereof I speak.) So for consistency's sake you'll need to add a few more for that speaker, but it can be just as irritating... er... face-slap-inviting... er... noticeable in print as in real life, which might be a real turn off when people are reading it.
Personally, I wouldn't do it. If that particular character would, though, use it.
(NB *pedant alert* -- "The instructions are in the top drawer." unless they are somehow encoded in lottery balls.)