I had finished 6 years(2004-2010) of my stay in US. My current company applied for my I-140(EB3) and it got approved. My H1 expired on Mar 2011 and I applied for an extension and I got it for 3 years(till Mar 2014).

If I find a new job and transfer my H1 how long will I get my H1 for?

If I visit India after shifting to my new job I had to get my visa stamped. Should I anticipate any problem because my I-140 is filed with a different company?

During stamping do I have to carry any paper work corresponding to I-140? (I actually have problem getting originals from my prev company.)