I think the key word here is LOVE you LOVE your car! How often do you think people say that? If the car has not been in a accident I'm sure you can find a professional to fix the high speed shake ( bent frame?). Depending on your finacial situation, why not rebuild the motor, tranny and suspension, what maybe $6k and while your rebuilding the motor add a few extras to take it to stage2 or more. You'll still have the ride you love, more power and the best of all no huge monthy payments unless your going to lease it, than that's another story.
I've had my wagon for 7 years and wouldn't consider a new 2013, that's just me though, some people love a new ride every 3 years that's why they lease. Think of yourself basically driving your car brand new off the showroom floor with suspension,tranny and motor upgrades ( the way it should have been built) and I think you probably keep it. Although I have no idea what condition the body or interior is in. GL.