Once you are finished with the paperwork, you will probably get the next flight to meet your spouse. You will need to have your passport with the visa stamp and the sealed envelope containing all the info for the customs to let you through.

Once at the customs, get in line under the United States residents/citizens signs. An officer will then take a look at your paperwork and you should ready to go within 30 minutes. He will give you some practical info about social security, etc.

Your file is going to be forwarded to the immigration authorities in the U.S. who will contact you several times by mail. First to notify you that they've received your documents and to give you an Alien number and application number, and then with your permanent resident card.

If you have checked the applicable box on your application, you should receive your social security card through mail as well. If not, you will want to get to your local office as soon as your have your permanent resident card. It takes about 3 weeks to get a social security card after you've applied and without it you cannot work (regardless of the fact you are authorized to work). Once you have both a permanent resident card and a social security card, you are good to go and can start working.