A) There is a driver's side and a passenger's side to it, mixing them up really increases the time involved and will cause you to swear at an unsettling volume.
B) I would have some of the circlips on hand; if one vanishes into another dimension, there really is no way to fudge something different into place [see above about swearing volume].
C) TEST THE NEW ONE so that you can avoid installing a dud and having to re-do it.
D) I doubt the hole-saw method really saves that much, but to each his own.

I think that the lore about the job is a bit over-done. The job itself is straightforward; the problems are along the lines of "How to I reach THAT?", "THIS is never going back in place!" and "The human spine does not bend that way." Don't psyche yourself out on it, it's just bolts, screws, clips, and wires (and vacuum lines).