JA+ you'll need.
As for Skins, Search around skins thread to find em i guess, they get put in some random places, though i do hear a new pack is comming out soon, so you might want to wait.
As for maps, what i just do is Google the exact Map name, and I usually get links to JK3files or file front.
like google seach the_academy_v3
and it will link you to File front for download.