I wasn't trying to sound ungrateful, so I am sorry if it came across that way.
No problem, you didn't.
I might be possible to somehow automate the copying of all tags over to a new field and then compying it back i guess, but I am not sure how that can be done.
I sounds like you still don't quite get what i'm suggesting, since you say you're not sure how to do it;)
if you have the names and genres (for example) of your files just how you want them today, I suggest you create new fields called Good Name and Good Genre (and any others you think might get overwritten accidentally). Select all the files that you are happy with the names and genres (can be your whole library, or a part, or just one file), then r-click, Library tools, Move / Copy Fields...
select Name as the Source, select Good Name as the Destination, and select Copy (leaves source) as the action. it will copy the names you are happy with to a new field.
do whatever you want to do in automating the importation of the mood, and whatever else it brings in, then once finished, use the copy / paste fields again, but use good name as the source and name as the destination and you'll copy back what you started with, assuring that anything that may have been changed by the import gets copied back over with the original data.
it's all very fast; at least it was the last time i used this trick.
it's also a good way to backup your known good fields, just in case something happens one day by mistake.