If you are referring to the engine cover, a crack will hurt nothing. It directs air around the engine to help keep it cool. If you are referring to the valve cover then the crack may allow oil to seep out, and will need to be repaired or replaced.
Tail lights are replaced by removing the entire rear plasic cover to the back hatch.
I highly doubt it. Unless the engine was damaged in an accident, the insurance would not cover it. But, you can ask them.
The valve cover on a typical engine is a non wearing part. If it were damaged it could be bent, warped or cracked and could be the source of an engine oil leak.
The ECU is at back of engine bay under windscreen beneath long plasic cover which is in two parts fixed by clips and two screws
Full coverage, minus the deductible.
there are cooling channels in the head. you might have a cracked head
warped valve cover. bad gasket. cracked valve cover cracked block
From engine compartment?- valve cover oil leak coolant leak-radiator/hoses from exhaust- black- too rich blue- burning oil white- blown headgasket, cracked head, engine is burning coolant
No, It Does Not.
What does the idle do? By "injection cover" do you mean air cleaner? That would make me think you're talking about a breather hose (AKA, crankcase gas recirculation hose) Those hoses sometimes also involve a filter and/or PCV valve. If the idle fluctuates or is higher than it was or than it should be, you might have created an air intake leak. (only if the hose you replaced is in between the air mass meter and the engine.) More answers might help: Is this an automatic? What size engine?
When facing the engine, you'll notice two small fittings on either end of the valve cover. The PCV valve is the one on your left. Unscrew the plasic cap and replace the valve.
If your engine is visibly leaking oil, you should remove that cover and try to find the source of the leak. But this is not something a typical do-it-yourself mechanic can fix, its possibly you will need new gaskets or worse (such as cylinder rebuild, or worst case replacement of a cracked engine).