Is there a way to change the actual song file but keep the 'info'?

Question

I have a compilation that took me a really long time to edit (by which I mean put the date for each individual song in because they were all released different years becaues it's a Bob Dylan compilation and I have smart playlists for each decade from the 50's upwards) and I want to change the actual file in itunes but keep the data, is there any way? It'd take ages to do again because it's a 3-cd album. I'm trying to change the file because the one I have is approx 200kbps bit rate and i want to have a different, 320kbps version that i've downloaded. I've tried opening the file in explorer and deleting it so that i can 'locate' the file again to the one i want to replace it with, but it changes the song title, album artist, and tags etc to the new file, whereas i thought it would just retain the information but change the actual file it played.
i've had a really hard time explaining this i'm sorry if it's unclear. i was just wondering if there was any way to avoid the painstaking process of googling each song to find its release date and manually entering it when i already have a perfectly organised album.
i can't find anything anywhere about this, presumably because i've no idea what the key words for the search would be, so i'm sorry if this is common knowledge.
thanks in advance

Answer 1

VBR vs. CBR isn't a concern as far as the strategy is concerned. As given it is slightly easier if the replacement files have exactly the same files names and folders as the files they are replacing (case doesn't matter) but if that isn't possible we can work around that too.
Not my area but I think CBR gives larger files and less processing overhead for the same quality, which is a somewhat nebulous term. I'm not sure there is any real benefit.
Yes a script is just another kind of a program.
iTunes gives each track in the database a unique ID and knows the path that the file is supposed to live on. If you replace the original file with a different file of higher bitrate that has the same filename then iTunes will use that new file next time it wants to play the track. When it does so it will also read the tag and update itself if any of the information is different.
The original function of the ExportImport script was to help someone else rescue play counts from an old library database. If works by scanning through selected tracks and writing out a text file that contains an ID for each track and the data that wants to be copied back later.
Here is a sample output from the export:
<#>iTunes Metadata - Exported 19/12/2012 20:03:58
<ID>E5C69360-306A28AF
<#>AC-DC\AC-DC Live\1 Thunderstruck
<Plays>12
<ID>7C1D487C-3414298C
<#>AC-DC\AC-DC Live\2 Shoot To Thrill
<Plays>12
<ID>0DCF32CE-1079174E
<#>AC-DC\AC-DC Live\3 Back In Black
<Plays>15
Each block consists of the iTunes track ID, a comment so we humans can see which track this is, followed by one or more properties. I can write you a custom version of this script but I need to know exactly which properties you need to save and then restore. For example Name, Year, Genre, etc. You need to compare a new and old version of one of your songs and work out which fields need resetting in the new song to make it match the old one.
Having saved a file with the information that would otherwise change, you can then delete the older copies of the file, or better yet move them to a backup location, then copy in the new versions. If the filenames match iTunes will "see" the new files automatically, otherwise my FindTracks script can normally fix the broken links. Once iTunes is connected to all of the new files you drag and drop the saved text file onto the ExportImport script to run the import phase. This applies the saved data to each track in turn.
tt2