10+ years should be no problem. There are some complaints about the injector ticking noise (only outside the car not inside), carbon buildup on the back of the valves and some delays in the transmission downshifting. I have the same engine in my Fusion with no issues. You'd really have to drive it yourself to see if you like the performance.
You can buy the warranty from any dealer including online any time before the factory bumper to bumper warranty expires.