hi! i thought maybe i'll just contribute what i can.
u record an action on what size u want to resize ur photo to.
then u go automate->batch processing. click on the resize action
u just did and batch process the folder of photos u want to resize.
quite easily done.
applies for other actions as well!
but be sure to keep a backup!
just in case u need the high res for printings or whatever else!
hope it helps!