I sent you a PM with links to expat sites that can provide some advice on taxes, including one site with forums for many countries. (You didn't specify which country that the income is coming from, just that it has a tax agreement with the USA).
While I was living in the USA I also had foreign income, from the UK, and TurboTax handled it easily enough as it was simple enough - pensions and bank interest. If the income from the Foreign country is not simple then I agree that professional tax advice is needed.
Retired in Jan, 2010 at 55, moved to England in May 2016
Enough private pension and SS income to cover all needs