could someone enlighten me in this disaster

There is one down in the lower front bumper quick and easy to replace.
There is an oil tank in the V of the engine where you need to remove the cylinder heads to get it in and out.

If you need to change to cooler in the middle of the engine under the manifold then I wouldn't even think ofit unless you have very confident in your mechanical skills. It is a very long and involved job, don't undertake it unless you know you can do the whole job.

Expect to be billed for about 17-18hrs for the job at a dealer. Both cylinder heads have to come off to change it.