C96326

Please could someone advise me. I am a British citizen married to an American Air Force member and we are stationed in Japan on military orders, my 10 year green card expired 9 months ago. I filed form I-90 electronically the other day and now I'm wondering if I've done the right thing as we are going to be in Japan for another 4 years so I'm unable to attend any INS interviews in the States. My question is can the INS process my green card renewal application via mail ? Also, if not will there be any problems when I return to the US in year 2008 with an expired green card, I was sent overseas on my husbands military orders.
I contacted immigration in Korea who have told me that everything will be fine as I'm allowed a one time entry into the US and can renew my card when I go back as I do have military orders proving why I left America but I'm worried that having been out of the States for a total of 8 years I might lose my status.
Please help if you can.