zhenghost, first lemme say, itll be the best money you will ever spend and it will be like nothing else youve ever done before.
as far as carrying a pocket knife on a jump, i can honestly say without a doubt in my mind that it would be utterly useless in freefall or under canopy. the only time actual blades would be used in skydiving is if you were doing CRW (canopy relative work) and had a VERY serious entaglement or maybe (and thats a BIG maybe) if you had a lineover and could clear it. in those situations a hookknife would be used, somewhat similar to the benchmade rescue thingy (if youve ever seen the frontsight hideaway knives these have the same type handles)
in most other cases if your main had a malfunction you (or your instructor if your on a tandem) would pull the cutaway handle which is connected to the cutaway cables which go through the loop sewed onto the risers at the three ring release point, the three consecutively smaller rings that you see on a skydivers shoulders act as a lever to give you a 200:1 mechanical advantage when cutting away. then, obviously, you would pull the reserve handle.
about the tandem incident posted on dropzone.com. from the details available so far it is assumed that they had a main reserve entanglement, which in this case was caused by the accidental dislogeing of the closing pin which holds the main container open, which then turned into a horseshoe malfunction that prevented the tandem instructor from releaseing the drouge to get the main to linestretch. because of this at 1900ft the cypress probably fired (if the reserve handle hadnt been pulled yet) causeing the reserve canopy to entangle with the horseshoed main which resulted in the fataility, however, this is all speculation (on my part). what is certain though is that once the pair reached terminal they never slowed down till impact. a pocket knife wouldn't have made one bit of difference in that case.
all that being said, skydiving is obviously NOT a safe sport, it is amazingly fun and for me it was and still is (40 some odd jumps later) a life changing experience, but it does have its risks.
if your still interested, obviously keep reading on the dropzone.com forums. and go out to the DZ near you to ask questions (skydivers are VERY friendly people)