I believe Kodewulf created a plugin to revert the nUI runes back to the BLizzard default after which they can be replaced by another mod. However, that said, this is not something I support doing. There's a FAQ here on the subject:
http://www.wowinterface.com/forums/s...ad.php?t=23943
The same would be true of the cast bar. However, neither of them should be in the center of the screen. They should be just above the dashboard. Can you please post a screen shot if what you're talking about? Just use the "paperclip" icon in the message editor or scroll down to the "Manage Attachments" button to upload the screenshot.
Now, the minimap, if you change the size of the minimap in its current location then it will overlap the unit frames in all of the unit frame panels except the solo panel. There's no room left to enlarge it in. So you really wants a larger minimap, you either have to put it into the info panel or not let nUI manage it at all.
The funny thing to me is that the actual minimap in the dashboard (not including the surrounding art) is less than 1/8" smaller than the default. I'm amazed by how many people see that as a big difference.