So I bought my Ergodox from Massdrop last summer. I had zero soldering experience, and zero gear.
I found the Youtube video much more intuitive than the Massdrop doc, but I sometimes had to refer to both just for clarification.
I could not get the surface mount diodes to work at all. I had maybe a handful of successes while testing the key presses. Removing them and re-soldering them had zero impact. I just went through and used the through-hole instead. I haven't read about anyone else having the same problem (granted, I haven't really looked), so I'm assuming this was just due to me not knowing what the hell I was doing.
The diodes were the most tedious part, everything else went smoothly and quickly, and after a few hours, I had a working Ergodox.
I would assume that if someone actually had previous experience with circuit board soldering, they could follow the directions and understand the intent much more easily than I did.
Having said all that, and after getting my Ergodox working, they now just sit in a drawer. I ended up disliking the layout of the keys. I find my Microsoft Surface to keep much more natural than the Ergodox. This could be because I don't have huge hands like someone else mentioned.