I am editing an answer and came across this line "Vote up and choose answer if I helped :D". Is it acceptable to ask the user to do this?
I don't think that is the best way to phrase it. A user shouldn't ask the OP to accept their answer, rather they select the answer that helped them the most. I would probably add a comment (rather than editing your answer) and phrase it more like:
Since you're new here, please don't forget to mark the answer accepted which helped most in solving the problem. See also How does accepting an answer work?
This means that you prompt them to accept an answer without requesting that they select yours.