I just got done replacing mine about an hour ago. I had a bad vibration when I revved back 3k rpm and never could figure out what was causing it until a week ago I noticed one of my header primaries was sitting on the motor mount. When I got them out they were destroyed!!!. The car is A LOT smoother now.
Look for header clearance, vibrations, clunking sounds, and also fan clearance.
If you have to replace them, it's not that big of a job, maybe 3 hours max.
