What else do I need?

I just bought WS6envy's Nitrous Works kit and have a few questions as to what I'll need. It already has the bottle, lines, window switch, and soelonoids. I bought a switch panel today off ebay that is made for our cars:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=33740&item=2474417422&sspagename=STRK%3AMEBWA%3AIT

I assume now that all I will need is a purge kit and new spark plugs? What kind of plugs should I order? I plan on running a 125 shot, which I figure should be ok on the stock motor -- that should be equivalent to a NX 100 shot since its measured at the wheels. Anything else I need to know, please tell me. thanks.

I would all ways run a fuel pressure safty switch to cut the nitrous flow if fuel pressure drops off.
Theres guys will most likly tell you to up grade you ignition system and run some regaped and modified NGK tr 7's.

If I upgrade ignition to MSD 6AL, will I still need a window switch since the Rev limiter will now cut spark rather than fuel?

yes you would still need the window switch. that makes sure you dont spray at too low of a rpm.