help!! would putting the wrong spark plug in wreck everything?

What was specified in the manual and what was in the bike? Some things won’t make any difference (like using a –ES instead of an –EG) but other things can make a difference. On some bikes there is vibration and the plug has to be a certain type to keep it from falling apart.

Frist of all you had the wrong plug (as you know). The reach is wrong (the length of threads) and who knows what else. The H is the reach and H stands for 1/2" reach, you need for that to be an E, which is 3/4" reach. Check to make sure the full length of threads in the head are OK since 1/4” of them were exposed due to the short reach. Here's a handy chart for what all of the numbers and letters mean: http://ngksparkplugs.com/docs/tech/design_symbols_plugs.pdf

I checked in Bikebandit.com for the OEM plug and they specify BR9EIX (see at: http://www.bikebandit.com/houseofmotorcycles/2002-kawasaki-kx100d/o/m141946#sch289585 ) which is a colder plug (9 vs 7) with a
High Performance Iridium electrode which helps with fouling.
.

The mfg obviously specified a special plug and you should run it but you could probably get away with the BR9EIX or even a BR9ES if your budget is tight. The ES has a std tip but they are cheaper and if your jetting is good they rarely foul.

Not sure what’s going on with the missing bearing. Which one? Was it never there or did it self-destruct when the engine seized?