Speaking as a CPA (though not an expert in expat tax) - you need an expert. If you're a US expat and your spouse isn't, things go from merely complicated to absolutely opaque. That said, the link below leads to a 136 page introduction to US expat taxes written for laypeople. The info is a little old (use at your own risk) but it should be a good start. See Chapter 17 for your question. That said, I think there are several threads here listing expat tax services. They may be expensive, but Uncle Sam has assigned brutal consequences to expat tax mistakes. http://www.uscms.org/uscms_at_work/w...xes%202009.pdf
For more up to date but less readable info, check publications 54 and 519 on the IRS website.