Chances are the actual cdi is good. Look into getting a new rectifier, pull all the connections apart, clean them, and apply some dielectric grease when reconnecting them. Make sure you get the ground location on the box clean, and you might look into making a second ground wire out of 6ga wire to go from the engine to the electrical box. I attach it to the drive coupling cover and just come straight across to the box and attach it to one of the cover bolts. I would also do some ohm testign on the coils to make sure they are good.
It's very common for those plastic pieces to break. You can buy new ones. They are kind of a pain to replace. You can also just use some 100% silicone to seal them. it will look like crap, but will water proof it.
If you don't have it yet, do some hunting, and download a manual for it. It will have all the specs for testing the coils, stator, and cdi along with a wiring diagram.