As a US citizen you're obligated to file (and possibly pay) taxes no matter where in the world you work and reside, no exceptions. It's the price of having US citizenship and access to the US embassy. In most cases you probably won't end up paying anything when you declare the tax you paid in your resident country, but that gets complicated with that country having a different tax year than the US (April to April vs calendar year). Get a competent expat attorney and pay for it to be done for you. There's also the FBAR which you might need to become acquainted with.
As for the retirement savings, lots of countries have their own types of retirement accounts that can be invested in as part of your paycheck. The caveat here is how to repatriate the funds when you leave before hitting your 60's. I haven't found a great way to roll those over to an IRA back in the states yet.