How to go about installing flowmaster 40 series?

I have a 2003 crown vic police package. I have dual exhaust and two cats on eachside. What size super 40 do i need and whatelse do i need to buy with them. I would also want to add maurauder exhaust tips|||If you order one for your specific model from the Flowmaster catalog it should bolt right in. I this is too complicated for you maybe you should bring it to a mechanic and let hm install it for you.