I have a friend who had around 2000 visitors per day to his website before a web designer with no SEO knowledge changed all his URLs. I've used the Wayback Machine and Google Analytics to determine the old URLs and I've done a 301 redirect and checked that it redirects properly.
My question is how long does it take before Google notices the redirects and passes link juice? And will those long-lost backlinks which where pointing to 404 pages count in Google Webmaster Tools - will I see a higher number of backlinks?
And last question, will I get a higher PageRank?