Timing chain problem, change of timing chain on Micra K12

Hi everyone,

I’m french, excuse my broken english.
I am here because in France there is no specific forum about Nissan Micra K12.
I have a 2005 Micra III K12 1.2 whose engine light comes on. The mechanic passed the car to the error code tester and told me that the return code corresponds
to the camshaft sensor and that the timing chain must be changed.

I want to examine visually the timing chain to see if she is relaxed (extended chain). I consulted many forums about K12 timing chain, including the procedure to change the timing chain, preferably without removing the engine.
To see the timing chain we have to remove the rocker cover. To do it, first, it is necessary to remove the air filter box and to disconnect the four ignition coils.
Until then, is my process correct?
Are there any particular points to pay attention to?

IsThank you in advance to those who could help me.