Not at all. For sure comes at the end of a sentence, or is a comment by itself, and means, I affirm that what was just said is true, I have complete confidence in it, or I have additional information that confirms it. Synonyms include "yes indeed" and "certainly." Surely is inserted for emphasis, like the word "really", but it is not used in modern language in the US except as a joke. In the parody movie "Airplane," someone says "Surely you jest!" (meaning "You must be kidding," but in Shakespearean-era language), and the response is "No, and don't call me Shirley!"