You should be alright hosing down your engine bay. If you use a bit of common sense you'll be right. Just don't spray too heavily around the carby, the dizzy, the spark plugs or anywhere water might be able to enter into the engine.
WD-40 or something similar always helps to dry up unwanted moisture if you do happen to get something wet. I would recommend spraying a bit of WD40 under the dizzy cap before and after you hose down the engine if you have some.
Also, NGK spark plugs are good, but really any suitable plugs/leads you can find at your local Repco/parts store should be alright.