What is the max trailer towing capability of a '03 Legacy GT sedan in automatic.  Also is there a plug and play set-up for the trailer wiring?

E-Trailer as well as others have trailer harnesses that are plug and play. Looks rated to 2k lbs to me. http://www.cars101.com/towing.html

If you're gonna tow that much, you should definitely have trailer brakes, and a transmission cooler.

I've done some stupid things towing, and I had a scary experience towing around 2000lbs  without trailer brakes on a subaru.

Do you tow all the time, or just want to know what the car is capable of for now and again? I would say 1500-2500 lbs based on yur experience. You could tow more, you could tow less.

 

What the car is rated for is how well it will hold the road more so than the physical attachment of the hitch and ball. A trailer is not going to break off the hitch, but it can push you around if it is not weighted or balanced properly. This is where driver experience comes in if it gets to that point.

Seadan or wagon ? the rating is not as importat as how mutch weight VS how good the backend of your car sticks to road the worry is having the trailer push your back end around or out on you a sedan is light on back end wagon better for towing.

It's a sedan, I have two small utility trailer I do dump runs with.  Have towed trailers with my '99 Honda Accord Ex 4 cyl. 5-speed for thousands of miles, so experince is not a issue.