If there is one thing you can count on, people have differing opinions. A precursory glance at almost any internet forum regarding oil change tactics, oil theory and how it relates to oil weight, oil change interval.
Most people I've come across believe the Mercedes 4.6 M278 M157 and M177 & similar can handle 100-200hp more with bolt ons, not even necessarily all of them. I personally have not seen a completely built m157 with methanol, bigger or billet turbos, dp etc. Usually people just do a few DP and a Tune stage 2 is most popular.
Getting back to the subject, the one guy I found, after hours of internet forums, facebook, etc, who didn't think the engines should be pushed past stock. When I pressed a bit he mentioned that the oil should be changed more often when tuned. I pressed a bit more, he mentioned that tuning did put stress on the timing gear and earlier engine revisions may have weaker timing components. And stated again the oil needs to be changed more often on a tuned Mercedes. He said every 3,000 miles.
3000 miles, that is and old school interval. Or perhaps one for someone who wants to protect their car and get the best out of it.
Approaching 5000 miles I quickly put this video together about how to change your oil as a general DIY guide using the newer suction techniques which these engines were designed in mind for.
Don't let the suction scare you away though. It takes less time to change the oil on many modern Mercedes than it takes to lift a camry in the air enough to get the oil filter under it. I would guess 7-10 minutes is a realistic estimate, with people being able to do it in 3-5 with a compressor to drive the suction.