When you use "Could you" you already have the sentence in the form of a polite request, so you don't need "please" there. Additionally, "please" is not generally used in sentences that are formed as questions. Instead, it is used something like this:
Please help me write an article.
Finally, the only answer I can give to your question is yes. I can help you write an article. Please submit only a couple of paragraphs at a time. (Not long ones.)