To start, I'm clueless in Excel.

I have my main spreadsheet that has names, addresses and country
codes. I need to compare the country codes from my main spreadsheet to
my country code spreadsheet that has one column with the three letter
country code (that will match the country code column in my main
spreadsheet), and then another column with the full spelling of the
country. I need to compare and replace the three letter code with the
full spelling of the country. How do I do this? My basic knowledge
limits me to creating a macro that searches for the three letter code
and replace with the full spelling, but there are over 240 country
codes and would take forever to create.

Can anyone direct me in the right direction to do this the right way?

Thanks,
Kim