At the top of the restoration forum are stickies. 4th one down is the DIY for boat restoration.
Links 14, 15, 18, 2, 3, 4, and 4a have all the information you need
Stop referring to the bad info on YouTube.
Your manual for your meter will tell you how to check a diode
You can get a diode from any electronic shop, or Amazon, or Newark.
Suggest a 5 watt diode
I buy them 30 at a crack...
Not sure what to tell you. It's not that hard. Are you using quality tools?
You can always suck the oil out the dipstick.
However if you have water in your oil, the motor is coming out