Is it possible to change permalinks structure?

Hullo,

I’m using wordpress with multisite enabled. So far I’ve got 3 ‘sites’ on the blog, with one more active than the rest, and the “Sitewide Tags Pages” plugin to pull all posts to the main site.

The problem/question:
I want to change the permalinks structure for all the sites from “/%year%/%monthnum%/%post_name%/” to “/%category%/%post_name%”

Can I simply go to Settings>Permalinks, change the setting and voila! it’s done, or do I risk breaking something in the blog?

Also, is this done from the main site or from each of the sites?

Cheers
ska