Great choice in a new gun.
As for the magazines, there have been several for sale lately in this forum's Classifieds section. They're usually advertised as "3913 magazines", as the stainless model is a bit more common, but the 3913 and 3914 both share the same 8 round magazine. The older 8 round magazines for the S&W 39 will also fit your 3914, but will protrude a bit from the bottom.
Seems like most custom holster manufacturers I've seen have molds for the 3913 series of handguns. You should have no trouble finding a quality pancake with a thumb break. If you're looking for a mass produced leather holster instead, I know Galco offers most of their holsters, including their FLETCH thumbreak pancake, for the 3913 series.
For takedown and reassembly, here's an online version of the manual:
http://stevespages.com/pdf/s&w_pistol.pdf
Unfortunately, some people find that the field stripping process for the 3rd Generation guns is a bit complicated to explain through just text and pictures, but easy to pick up on in person. If you still can't figure it out from the manual's directions, your best bet may be to find someone in your area to show you how it's done.