Current: Education= MS in materials Engg and BS in Metallurgy . Job= Research engineer in R&D. H1b second term valid till 2012. GC= EB2 (Advanced Deg) I-140 approved PD Nov 2007. LCA code 011( metallurgy and materials engineer).

New offer= Operations Engineer (for Materilas science) in same company, same location only change in title,dept and $ by 7000. Job duties will be same as my current job in materials sceince.
1)What is the process to change? Invoke AC 21?
2)Notify USICIS with just a letter indicating job duties are same between two jobs. What doumnents for same should be sent. I am concerned with recession if DOL issues RFE etc.& Labor has to be filed again
3) Since same company and same job duties can we leave the case as is and just file for AOS when time comes. - Advise