Deleting duplicates after converting to AAC.

iTunes creates a new file in the indicated format, and leaves the original file intact and in place. You can then manually decide to keep or delete it.

If the original was in any Regular playlists, you can manually add the newly converted file in its place; that will not happen automatically either.

As far as "AAC or Apple Lossless, whichever is better for quality and space," AAC is better for space and Apple Lossless is better for quality. The majority of people nowadays use either AAC or MP3 at 256 kb/s, but if you prefer lossless, go for it.

Brian452 wrote:
Is there a format that you can burn cds which will automatically populate the song titles and album info.. etc.. when it's uploaded into itunes?

Sort of! When you insert a CD into iTunes, and you see the track information pop up, that information is not on the CD itself. It got there by iTunes making a query to the Gracenote/CDDB database, and finding a match for the CD's particular combination of tracks and lengths.

If you burn your own CD, and want to put the information into Gracenote, it is pretty easy. With the CD still in the drive, use the command Advanced > Submit CD Track Names. Gracenote takes a while to process, but by a day later, any iTunes in the world should be able to know the track info for that CD.

(There is also a thing called CD Text, but it is not widely enough used to solve the problem.)