Flac to .wav or Re-flac

Have allot of .flac files, I would like to set a standard on,
say setting flac -3 --replay-gain....etc..etc

Now, can one re-flac a already .flac file again into to this standard setting 
I want to use... or does one have to un-flac the file into a .wav file first.

if so, how does one uncompress a flac file back into a wav( without) lossing 
its meta data.

Thanks -
Richard