Er. I'm afraid the scripts would have to be of the DIY variety, as I don't think anyone's formally written up and distributed anything yet.
Personally I just type 'for m in *.mobi; do mkdir "${m/.mobi/}"; mobiunpack "$m" "${m/.mobi/}"; done' directly into the Terminal whenever I want to do a batch unpack and I'd probably run sed or something similar the same way for the batch search and replace before regenerating the .mobi.
Sorry for getting your hopes up.
Calibre does have a "bulk convert" mode if that's of any help.