iPod Cleaning up my library... I have a problem.

So I was just cleaning up my library a little and importing some songs I needed to add. I have been trying to make my library clean for some time now and the new add album art function in iTunes gave me motivation to fix some things. Here is the issue...

I have a lot of playlists, I never really delete them as I keep just adding more. I want to convert a lot of songs to ACC which are currently MP3 files. When I go to convert them it makes a copy and naturally that copy is not put in place of the existing file in a bunch of playlists, it is just added to the library. Is there any sort of plug in that can help me with this. I want to just convert all the MP3 files in my library and delete them but that would remove them from playlists. Can iTunes go in and insert the new files where the old ones are?

Also... does anyone have a good plugin website? I can't seem to find one. I found one before but I cant find it again.

There is a PlugIn found on Doug's Apple Scrips that seems to do what I am looking for. It is not perfect and takes a little getting used to but works as long as the songs are not in multiple playlists. You can have it replace all the MPEG files in one playlist if you use the re-name command it offers.

The plug in is called Quick Convert.