A: You really need to contact an immigration attorney.
From what I understood from your question: he obtained his green card based on your marriage and obtained a conditional 2 yr. green card. He then left country and remained overseas.
In order to remain a permanent resident, a conditional permanent resident must file a petition to remove the condition during the 90 days before the card expires. To remove the conditions on a green card based on marriage, you must have filed Form I-751,Petition to Remove the Conditions of Residence.
During this time there were residency requirements, which your husband failed to meet. There may be other remedial measures for your husband at this point but more information would be necessary. You really need to contact an immigration attorney.
A: It really depends on the specific circumstances of your case. I would recommend that you contact an immigration attorney immediately.
Generally, if a person overstays their visa, they will be subject to the 3 and 10 year bars provisions of the law which prohibit applicants from returning to the United States if they depart after having previously been in the country illegally.