I don't have a WIS setup running yet, is someone able to pull the WIS documentation on how to R/R the camshafts on the M156? I'm going to be removing them to fix my cam phasers and also going to put in the SLS BS buckets while i'm in there, but I only have experience working on small 4 cylinder japanese import engines, and most of those have keyed camshafts and cam gears. I'm worried about the valve spring tension when I remove the cam caps and about correctly timing the cams on reinstall so they're not 180* out. Just a quick look at how the keyways for the wrench and locking tool for the cams looks like it's possible to have the cams 180* out.

You need the kit that indexes and holds the camshaft properly. If you use the rear alignment tool properly, you can't install the cams 180* out.

I have the kit! thank you for confirming they can't be put in 180* out with the tool.

Just make sure that the tool fits flat on both sides. The slot for the tool is asymmetrically cut on the back of the cams, so you can get them pretty close by eye once you know what you are looking for.

Also, make sure that tool is flat before installing...some of the cheaper sets have been known to have the rear alignment bar bent.

yes the rear of the cams are slotted off center so the rear flat bar only works one way so you can't be 180 out - be careful the cheap Chinese made ones are not head treated and the bars bend easy (or come bent as I experienced once) just check and flatten it if necessary and recheck when using it as you can bend it tightening the phasers.

As for valve spring tension, just loosen and tighten the cam bearing caps a little at a time in a pattern don't just take them off all at once and same going back on.

I think taking photos of the cams when the removal cam kit is installed and when you remove the cams I would loosen the cam caps, use a small socket set and then slowly loosen all the caps to keep the cam flat at removal.
For install tighten by hand socket the cam caps to slowly keep the cam flat (parallel) with the head socket until all the caps are touching ready for torquing.

Valve/cam Timing tools -> JTC Auto tools 4243 auto link Benz AMG Engine timing tool set (M156) (need two of these to do the job)