MBWorld.org Forums - Undercarriage cover question and GLS 550 question

I drove over a curb by accident and notice this fiberglass cover underneath the passenger side of my GLS550 tore/broke a little (pic attached). What is the purpose of these 2 square shaped holes and is it necessary to get it replaced?

Anyway, does anyone know if the 550 engine is the same as the AMG V8? They look very similar in design. Other thing I hate is the eco mode auto start-stop thing which I cannot understand why I would want my car to stop for half a second as I'm waiting to make a turn. I'm looking at a hack from Vladimir on ebay that can reprogram it easily through the OBD port: https://www.ebay.com/itm/252811119026. Also, does anyone have an opinion on Mobile 1 0w-40 vs. 5w-40? Can i really go 10k if I use full synthetic? My goals is to keep this car for life. Will I be able to get 300k miles out of the 550 engine? When it comes to gas, I filled up my 350 once every 2 weeks and the 550 is about the same. I also noticed it likes to lower itself sometimes after a drive...when I park and get out I notice it lowering slightly. Thanks!
https://cimg3.ibsrv.net/gimg/www.mbw...4328069b0b.jpg
https://cimg6.ibsrv.net/gimg/www.mbw...4bd93505bf.jpg
https://cimg0.ibsrv.net/gimg/www.mbw...59b45e9142.jpg
https://cimg7.ibsrv.net/gimg/www.mbw...5c0cec3da9.jpg