Just in case you didn't find the answer after all, I'll give you my $0.02 worth.
PPAP requirements are ALWAYS driven by your customer. You are required to inform them of the change, and you MAY suggest what the changeover will require; anything from an email acknowledgement and approval of the change to a full blown PPAP submission, with performance testing, etc. I have gone through both extremes with customers.
Don't, however, ignore the customer approval. How they choose to give that approval, and what evidence they require to give that approval is dependent on how good a salesman you are