Do I need a new head ?

[ktbtrucking]

Long story short,
truck is volvo with dd13 with 550k miles

Long cranking and hard start. Driver claimed that truck runs weaker and weaker.
Changed all 6 injectors and injector cups.
2 months later valve broke down and damaged the turbo.

Shop claims need new head and new turbo.

Any thoughts. My knowlege is limited on dd13 but when injectors are being changed you have to remove camshaft and than do overhead set. ( I believe so.)

Is it possible that shop did something wrong, they are new in bussines and still learning.
No blaiming them at all just need some guidance if let them put new head and turbo.
Do I need to adjust turbo actuator when reinstalling new turbo?
All help is appreciated.