w220 s600 ignition coil
 

car started to knock took it in the mechanic said its the coil on the driver side. he already tried replacing the plugs and didnt work so i now how to replace the coil.

now are both sides interchangable?

whats the best way to go about that?

used or new? or is it took risky? where is a cheaper place to buy them?

is the 2003 and up twin turbo coils still good on my 2001 na?

how hard is it to take the engine apart and get to the coil i saw the engine taken apart and seems to be something i might be able to do...

help me!