1. Preparing the MMU2S upgrade kit

If you bought the mks3+ and the mmu2s together like I did, and especially if you are new to 3d printing I strongly suggest building the printer without the MMU2S , getting it working, making several dozen prints and THEN add the MMU2S. But if you are stubborn like me and hate having to redo things the other comments are correct and you can combine the extruder build with the upgrade extruder steps from the mmu2s and then carry on and save a lot of work dismantling the printer once it's built to add the MMU2S unit. Read both assembly instructions through and you should be able to figure out which things get changed out during the upgrade.  The problem for me came after it was all assembled and I tried to get the 1st layer calibration done. It just made a blob at the start point and then would jam up in every conceivable way possible.  So I tried just printing the example prints on the included SD card... Got lots of piles of spaghetti and more jams. Printer started some prints a couple inches off the bed and all kinds of other weird fails. Four straight days of dismantling to clear jams is no fun and I was going to scrap the mmu2s and build the stock printer so I went back to review the assembly instructions for how much work that was going to be and found the calibration section instead. My mmu2s sensor was set too close to the ball and was falsely seeing filiments loaded when they weren't, my ir sensor was off just the tiniest bit and that was causing false readings as well , and the superfinda was set too close to the bed, maybe a full milimeter.  Also I was just doing tests so only loading one filiment, which means the tension access the idler was all wrong. Used some scraps and loaded them in place just to do some tests.
Very first try was poor quality but actually usable to adjust the first layer properly, second try I got it dialed in very nicely. Then I went looking for mmu2s example files and printed a 2 filament test file and a mono test file with beautiful results.... And absolutely no jams since getting all the calibration done properly. Support menu - sensor info is a life saver, with the calibration help that explains what the sensors are telling you/the machine.
 
Best of luck and happy printing.

Hi there,
I have a Mk3S I'm about upgrade tu MMUS. I've got, as required, an Mk3+ upgrade kit and a MMUS upgrade kit. I can see the long way would be to follow the Mk3S -> Mk3S+->MMUUS instructions, Can you confirm that following 2B then 3B then Chapters 4-9 is effectively the same saving the time of assembling then disassembling the MkS+ extruder

Hi there,
I have a Mk3S I'm about upgrade tu MMUS. I've got, as required, an Mk3+ upgrade kit and a MMUS upgrade kit. I can see the long way would be to follow the Mk3S -> Mk3S+->MMUUS instructions, Can you confirm that following 2B then 3B then Chapters 4-9 is effectively the same saving the time of assembling then disassembling the MkS+ extruder

This video gave me  agreat understanding of how the mmu2 works and a better discription than I have seen anywhere of the buttons and what they do. - https://www.youtube.com/watch?v=n5AAarO-3J4
Wish I would have found this before I built but glad I found it as I started working with it- it answered alot of questions I had forming in my mind ... Great 3d Printer great addition for multi material ! 

Is there a download for the complete assembly manual I can print? I prefer to work from paper and refer to the online manual only if I get stuck.