My six-year term of H-1B is set to expire on 8/30/12. I have an EB3 GC application with my current employer, with a priority date of 12/27/10. My I-140 was approved in Sept 2011.
Because my I-140 has been approved, I will get to extend my H-1B for another 3 years, instead of 1 year.

What are my options if I wanted to switch employers?
Can I switch employers while I am on the 3-year H-1B extension?
Is there a way I can keep my GC priority date with a new employer, considering I have not been able to file I-485 yet?

Thank you.