Help writing my first apex trigger in Salesforce - I have a simple use case in mind

Hello World!
I have a use case that requires a trigger and it sounds about as simple as it gets. We have an external application called BrightTALK integrated with our Salesforce org. Trouble is, we use State and Country Picklists and BrightTALK tries to push Leads into our Salesforce org with Country names that do not match the countries in our Salesforce org. As far as I know, there are two ways to tackle this issue. 1) Change the list of Countries in our Salesforce org. 2) Write a before trigger, which, if I understand correctly, could change a Country value like "China (Hong Kong)" into "China", which our org would then accept because the value matches a value in our State and Country Picklists setup.

I have never written a trigger before, and I took one programming class 10 years ago. Does anyone have any recommended places to start, sample code to look at, reference material to refer me to where I can see the methods available to me in an before trigger and learn some syntax? Any help is much appreciated.