My wife and I are currently going through this process.

In summary, your US citizen/resident spouse will have to submit form i-130 and wait for it to get approved. Once that's approved, pay for the Visa fees and submit form i-601a. Wait for that one to get approved also. Finally, go to a consular interview in your home country to obtain a visa. If every thing goes well, you'll come back as permanent resident.

Usually, if your i-601a form gets approved, you have very good chances of getting the visa approved and coming back to the US. From what i've heard, you wont have to spend much time abroad for the interview. Not more than 10 days, usually.

Check out the Official I-601a Thread:
http://dreamact.info/forum/showthread.php?t=78973

Talk to an experienced lawyer.