H1B Amendment Process from India & Timelines


Can someone please clarify my queries regarding H1B Amendment.

I have H1 stamped in Jan-2016 and working in India. My LCA is posted to Client1 & Location1. I moved to other project at offshore and reporting to Client2 and new location would be Location2. I was asked to go for amendment for change of client and location.

My Questions:

1. What is the timelines for normal processing and will there be any difference with Premium Processing?

2. Do I need to wait for 2-4 months, waiting for the confirmation receipt from USCIS to travel?