InvisibleMan

I have just taken my '96 Sport to the subaru garage for a service. They have however given me a very large bill of what needs doing. I cant list them all here but various things seem to be leaking or need replacing, each at about £100 each?, i have no idea so cant dispute them.

The main problem i have is that after a journey the car needs a 30min rest period before restarting the engine else it wont start.
They have told me its a:
Crack sensor £88
Knock Sensor £77 (which im sure ive been told is merely a bolt on the top of the engine???

Advice asap would be appreciated!