I learned how brittle those hard lines are when I replaced the check valve. Lucky for me, I only cracked the end, and the new check valve was longer (aftermarket aluminum one).A job that is remarkably easy to do when the engine is out of the car!
On what to do:
Disconnect the main harness and use a bungee cord to hold it back and out of the way
unplug the hard line brake booster line from the manifold and from the vacuum pump (or tcharge air tube if manual) and leave it loose. you don't want to snap one of those when you pull on things. (yes, I did the first time I did the job)