I would like to share the great news with those who are waiting for GC. I would like to thank all those who helped me here, including Pjiang laoshi and the others. I came to USA 2003 and did not apply for GC until Aug. 2009 for some reasons. I used DIY. Every thing is not as hard as I thought. I-140 was approved in 3 days after it was filed using PP, and I-485 was filed a month after the approval of I-140 (for health check and birth certifcate preparing, etc.), and took 2 months to get my I-485 approved.
Good luck for every one.
I will still visit here to encourage you.