Answers

First of all, will the electrical box be able to support the new fan? A paddle fan takes a special box rated for the extra weight. You can get one for an "old work" set-up and use the same ceiling cut-out. It's a little tricky getting the old box out, especially if there are a lot of wires coming into it.

In all honesty, hire a professional electrician. They will know how to install the right equipment to be sure your fan remains where it belongs and is safely wired. Good luck!