yep, you got it man!
those float bowl drain screws are notorious for leaking because all they have is a fiber gasket, and the threads that are cut into the bowl and the screw are not the best.
the ngk plug alone will give you an improvment over the stock plug (which is junk).
your next improvement shoudl be to replace that stock el-cheap-o spark plug wire and boot.
it's simple to do, cheap, and it will give you a little improvement on how it starts and runs. The stock apsrk plug wire is nothing more than a (seriously) few strads of copper wire inside of a cheap, hard rubber peice of insulation.
get an automotive spark plug wire with a rubber boot to replace it with.
the stock wire just (in 99% of them anyway) unscrews from the cdi bix by twisting it. there are some cases where the wire is glued into the cdi box, but it can be cut out.
there's a screw inside the cdi box (once the wire is removed) that the wire screws onto.
so, unscrew the stock wire, and screw the new wire on....simple.
this will also allow you to get a longer wire to re-locate your cdi box to clean up some of the wiring (if you want to).
I have the cdi box hidden under the engine on one of my bikes, and low on the seat post on my other bike. it looks nice & clean because all of the wiring going to the cdi and to the engine is hidden under the engine.
the only wire that runs up the frame on both of my bikes is the kill switch wire. (and the throttle cable)