In iMovie 11 can I color correct multiple clips at once? If not, can I copy a color correction and apply it to other clips?
Yes you can. To select multiple clips, hold the command key and select the clips you want (you can click on them a second time to deselect them). Then click on the "i" to pull up the inspector and manipulate at will.
The command-click thing works through most of the operating system (and applications), so for instance in Finder you can command-click to select multiple items, then open them all, or delete them all or whatever you want
Just drag and drop... it's pretty much all drag and drop (and usually more obvious than you think)
If you wanting to move the audio from within the clip, you'll need to extract the audio first - just search the help files to find out how). If you wanting to overlay a music track or another audio track, just drag it in and drag it around to move it. Note here that if you drag it on to a clip, it will make the start point where you drag it to. If you drag it into a blank space, the whole background will light up green and then it will play it over the entire movie. Command-z to undo if you make a mistake, or just select it and press the delete key.
This is a great place to get started: Apple - Find Out How - Movies - iMovie
Seems you can actually (had to check that one), I've just fiddled with it for a minute, so fiddle around to figure it out (and pop in "paste adjustments" into the help menu to get more info)
If you make adjustments, then Edit menu --> copy (command-c will probably work), then select the clip you wanting to copy to and go to the Edit menu --> Paste Adjustment, and then select the appropriate adjustment to paste