Sorry but I've been around these vehicles for going on 10yrs and never seen a bad one. I've seen the code plenty of times but I never once had to replace the cat. Also turbo seals? Even that screams PCV issues.
So, if we are tossing around numbers. 99% of the time it is not the cat.
Ohh I am considering the time, as I personally don't want to do the PCV system over again. With the stock PCV hoses, they are pure junk. I actually us copper tubing for the large tube and fuel line for the vac line. Correct on the trap, most times it's much less of a pain to just swap out a new one. But $200 bucks? I would be broke if I spent that on the amount of these systems ive replaced in my life time.
As for the timing belt, like I said, those dayco rollers are identical to what you pull out of your blue box. Again, water pump is the only unknown for me in that kit, but I usually get the rollers and belt only kit and buy the pump seperate, either GMB, or HEPU.
To the OP, your dealer must have thought the PCV system blockage was turbo seals, as these turbos are near bullet proof. Ive heard of and seen only a very few of them going bad. 300K to 400K miles with no issues with the TD04s. 99% of the time it's diagnosed incorrectly because the tech doesnt understand crankcase pressure.
One tip that isn't easily found online is to leave the exhaust manifold and turbo in place when doing the head. Other then that, just look around for guides and info on the process. Only a torque wrench is needed for "special" tools. Make a degree wheel out of cardboard or whatever else.