Here is my thread on the Magnaflow 14" on a Sport install. http://www.ramforumz.com/showthread.php?t=148502
You will find a sound clip, install information, and sizing charts. I hope it helps.
To answer the question, yes it is 3" in and duel 2.25" out. If you go with a 2.5" out you will need a reducer installed.
Figure on about $200-$300 for install and the muffler; $200 if you do it and $300 if a shop does it.
Parts and consumables: $75-100 (extensions, clamps, reducers, bends)
Shop Install: $150-$200 including parts.
*Yes, it can be done cheaper, but not much.