Re: Converting single conductor to 4 way
The coil wire is super-thin, thinner than human hair. But you won't be dealing with it unless something goes horribly wrong. But Dr. Nuke's basic point is correct, it does require a steady hand and some experience working with small, relatively delicate wiring.
Each coil has two leads, start and finish. The start lead typically comes out of the bottom of the bobbin at the end while the finish lead comes off the side of the coil. These coil lead wires are pretty small, but not terrifyingly so, so you can work with them. They're the same size or slightly larger than the 4 wires coming out of the end of a 4-conductor lead.
The trickiest part is separating the two leads that are soldered together. Best to use desoldering braid to pull out the old solder so you can then easily pull them part. You definitely don't want to be yanking these leads, especially the start leads! Yank the finish lead out and it's a bit of a hassle but you can fix that by twirling the coil wire around the end again and re-taping the coil. Yank the start lead out and that coil is dead and gone forever. You'd have to gut it and rewind it.
See this chart, and you can use whatever color code you want, including Duncan's:
http://www.guitar-repairs.co.uk/guitar_pickup_colour_codes.htm
It gives you the start and finish for each lead and what color to solder it to to match the manufacturer's code you're most used to.
Other things to deal with are taping off the solder joints between the 4-conductor wire and the coil leads. These taped joints need to be kept fairly small so they can be tucked out of the way to keep that end of the pickup from being bulky when you put the surround tape on.
Also, the bare wire is soldered to the baseplate.