Spark plug housing or nuclear triggering device???

Alrighty then...I have a 2000 Honda Odyssey 3.5 V-Tech. I just had it in for 105,000 mi check up and was told that recommeded maitenance included changing the plugs (which they wanted $250 to do!).
So I says to myself, "Self, you've changed plenty of plugs in your day so why don't you just buy the plugs and do it." So, I checked out plugs online...not bad...~$11 for double platinums. Next step, check out access to the plugs...popped the hood and looked down at the engine block...HUH!?!?! I can access the "plugs" alright, but I have never in all my engines seen what I'm now starrin' at. Where there would normally be a cable and plug, I see little square plastic components anchored by hex-cap bolts with three conductor cable comin' off of each of 'em...(pause while scratching head with furrowed brow). So, being a curious monkey in part, I head for the tool box and come back with the necessary gear. Proceeding with caution...cable component disconnects easy enough...hex-cap bolt
is simple enough...grasping the component...twisting gently it slides out of the engine block. What I now hold in my hand appears to be a triggering component for a nuclear device! Attached to the backside of that boxey visible exterior is a black tube about 5' long and 3/4' in diameter. I'm assumin' there is a spark plug in there somewhere/somehow, but I can't see how the component comes apart. Now, I have no problem admitting when I'm in deep water, so I slide that tube back into the block, secure the anchoring bolt and cable clip, and then close the hood while saying loudly, "Well, that takes care of that...(just in case any of the neighbors happened to be watching what I was doing). So here's my question - can anyone enlighten me as to what I was holding in my hand...and is there a spark plug inside of it that I can replace myself??? Many thanks in advance for any insights shared.

Not 100% sure, but I would suspect that you were holding the individual coil unit for each plug. Honda uses a combustion chamber with the spark plug in the very center, so there is a tube coming up from the head through the valve cover. The spark plug is in the bottom of that tube....See the following:

http://www.hondaautomotiveparts.com/auto/jsp/mws/prddisplay.jsp?inputstate=5&catcgry1=Odyssey&catcgry2=2002&catcgry3=5DR+EXL+LEATHER&catcgry4=KA5AT&catcgry5=IGNITION+COIL-SPARK+PLUG

Hope this helps....Glen

Thanks Glen. That is exactly what I discovered after thinkin about it a bit more. I didn't know the upper unit was teh coil, but I did figure out that teh plug must be seated in teh block at teh bse of the "tube." I confirmed that today with a socket and extension. Thanks much for the link you send also -
nice to know I can get the coils if needed as well.

Best regards,
Howard (VanGuyII)