Donnie
I would say the Zkit60 kit build is more difficult mechanically than it is electrically. You do have to populate, solder, and trim / clean 3 circuit boards, but they are straight forward and "expected"...there is nothing new here.
Mechanically, there is some new stuff that the average person has not done before. Holes most be drilled in-between the heat sink fins for bolts that mount the circuit boards and bolts that mount the power transistors in a "close enough" position so the leads can be bent at 90 degrees so they touch the proper eyelets on the circuit boards so they can be soldered in place. There is even more to it if the newer, smaller, chassis (which I recommend) is used such as this one:
https://www.ebay.com/itm/2412C-Full-Aluminum-Enclosure-mini-AMP-case-power-ampli...When building in this smaller enclosure it is best to mount the two audio boards "mirror image" to each other (so one is mounted up-side-down) so the large capacitors almost touch - this leaves plenty of room (where the capacitors aren't) for the power transformer. Again, this is all mechanical and just requires a little planning before the drilling starts. And even if you goof it only means a few extra holes that can be plugged (epoxy glue) and touch up painted.
I recommend buying the circuit boards and parts from Decware and then buying the chassis yourself from Ebay. That way the chassis is only shipped once.
Multi-meter wise, if you follow the directions you shouldn't have any trouble. There are current measurements and voltage measurements but they are spelled out clearly. A bit of effort went into coming up with a way to set the bias and balance without an oscilloscope, signal generator, and dummy load and it seems to be working well.