My company is planning to send me for an overseas assignment for two years. My green application is pending.

Details:
EB3
PRIORITY MAR 2007
I 140 APPROVED
485 pending
EAD/ AP 2010 July

EB2
Labor approved
I 140 pending-Jan 12,2010

H1 B till July,2012

My question
1)Can I take the overseas assignment and maintain my green card application,H1 B and EAD Status. What do i need to do maintain all of them.
2)Do i have come to the US yearly ones to the states to renew my AP and wait for the renewal AP to be approved before i leave the US.
3) Does the payroll has to be in the US office or it can be per the overseas office. Where would i have pay taxes.