About To Migrate To Multi-Database

Just wanted to make sure I have everything in order before I start. I've already backed up my database, it holds about 600 blogs. I've downloaded the 0.6.2 version and will be using the 256 db option. I've also downloaded drmike's 256 db creation script. I wanted to make sure of a few things before I start, just in case...

I assume I can use the 256db creation script with a pre-existing install? Just fill in the cpanel and db user information, change the extension to .php, upload and run it via web browser?

And for the move_blogs.php script, there's a configuration for $newdb_prefix = 'newdbname'; and let's say the original database name was user_wp and I wanted to name the rest of the databases user_wp1, user_wp2 etc. - would $newdb_prefix need to be set as 'user_wp' or am I lost?