It certainly does come across as a horrific prospect but as someone who has disassembled most every era of pin now, multiple times, I will say..it's not so bad as long as you take lots of pictures, label everything you can, ONLY unplug what you truly need to unplug (unfortunately on Metallica that's a *lot*, including every damn thing in the head), and otherwise document everything you can. Go slow on reassembly and double-check your work on anything you're not really, really sure on. Most of the time it's pretty difficult to plug things together that shouldn't go together but it's certainly possible.
Metallica had a few confusing things that I got caught by--black/white plug going in to double blue plug by the transformer, interlock switch connectors (which I labeled top to bottom but forgot to take note of which contacts on the switch were left open; had to consult the manual and it confused me so I ended up plugging it in how I thought was backwards but actually correct -- lol) and my GI plug slid down into the loom and I missed plugging it back in, but otherwise it all went without a hitch. Easy peasy, but definitely intimidating as I went further along and realized just *how*many* damn plugs I was dealing with.