Universal Widget Search & Replace

After developing a website, committing much content to it, using multiple custom control widgets, and about to give live... a decision has been made (not mine) that some CSS class selectors need to be re-named, so that those class names can be re-used for other styles - i.e. someone has changed their mind - ugh!

Unfortunately, these class selectors have already been used throughout the site, on multiple pages, on multiple widgets of each page, and on multiple properties of each widget... a real nightmare scenario.

So what I now need to do, is write a utility to blast through all of the pages, check every widget on the page, inspect every property on each widget, and make a universal replace wherever a specific string is found.

Anyone got prior experience or bright ideas ?