I had my trusted mechanic check the error code before I go to the dealer to have whatever needs to be fixed under the CPO warranty.

The error code was 143 Tank leak, this does not mean that gas is leaking but BMW will have to test the entire system for possibly a vapor leak. Let's see.

In regards to the coolant, the plug seemed to be the problem, there is no coolant leaking or decrease in level, so I guess that is fixed. We also checked the oil just in case (for the head gasket problem) and it looks good, just a little condensation for which I will keep an eye on and address with the dealer (better be safe than sorry). The check engine will not reflect this problem should it happened. I guess it all happened at the same time, the coolant leak and check engine light right? - I keep all posted on what happens when I go to the dealer hoping my experience can help someone else. After all this is why we are all here right?

Thanks to all for your input.