I got the muffler and installation including a new 2 1/2 tail pipe done for $215 at a local muffler shop. It took the shop 30 minutes to remove and replace the old muffler and get me out the door. I have been very happy with it although I second guess having not gone ahead and done the complete system. I would recommend that if you can afford it, get the complete exhaust done. I have been told that the performance gains with the complete kit are nearly double what you get with just the muffler. I have not seen any physical documentation to substantiate this though. I was impatient and went with what I could afford at the time. I hope this helps.
From looking at Magnaflows website, it looks like you have done a "Catback" system. Their site for the Sport Trac just shows their muffler and a single exhaust pipe out the back. Mac, is this not what you did? What differnce do you see from the term "Cat Back"?