If you have an ohm meter, your dad will know how to use it, try this:
Use Low Ohm-Meter Scale About 200 Ohms
Magneto Coil
1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.
CDI
Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms
Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms
As for keeping water/dirt out. Make sure the gasket is good or seal it with a small bead of silicone and fill the hole where the wires exit the case with the same silicone sealer.
Tom