Moving Blog - Best way to rewrite or redirect posts to new home?

Hello

Now that we have a nice WP MU establishment I've been tasked at looking at consolidating some of our standalone blogs into this configuration.

The plan is I will export & import the data and files from oldblog.com/subject into blogs.new.com/subject

I'm wondering what the best method for redirecting posts from the old blogs to the new blog is? As the old blog is very well established and generates alot of traffic from the search engines

So for example user finds a post in google on their subject that goes to oldblogs.com/subject/2010-06-12/post-about-something/, then I'm assuming you can do some sort of redirect that then takes it to blogs.new/com/subjects/201-06-12/post-about-something? (http://wordpress.org/extend/plugins/redirection/ along these lines?)

Now this is made slightly more complicated by the fact that another blog I'm looking to consolidate doesnt use pretty permalinks just the index.php?p=1234. I'm wondering if I should switch it to use pretty permalinks now so it updates the search engines as the query string will still work regardless of what permalink setup I'm using

Has anyone had experiance with moving blogs to another domain/location and then handling redirecting posts?

Thanks

Doug