Hyundai Sonata Catalytic Converter Replace/Remove

Just Wondering On A Scale Of 1 To 10. How Hard Is It To Change The Rear Exhaust Manifold And Converter? Is It Something I Could Do Without...

I Replaced One Of The Three Converters. All 4 02 Sensors. Code Po420 Came On. I Used Catty Clean Worked For A Couple Days Then Code Came...