It's been awhile since I took the grille out, but IIRC there are clips along the top you need to stick a screwdriver blade or similar into to release. Once you see how they work it's really easy. I think the bottom just sits in some tabs/holes.
If I'm wrong it's because I'm confusing it with my Impreza. :crazy:
For the fogs, you'd have to do some rewiring to bypass the signal from the headlight switch. I don't really know why you'd want to do this, as the fogs really should only be used with the low beams anyway. When I install fogs or driving lights on any of my cars I always wire them in with function of the low or high beams. Subaru just adds a manual switch to turn them off completely.