Yeah, they list them for the 2.0 Mazda3 but it's not the same size as the OEM filter. The 3 and the Pro have the same size filter base but the 3 is longer. Check it out, though. They may have wised up.
IIRC, I didn't use any gasket sealer. It's a crush-type gasket, so none should be needed.
I don't recall the torque specs but if nobody else jumps in here, I'll look them up for you when I get home.
Just fyi, the folks at Mazda6Tech made a little how-to (with pictures) if you want to have a look.
http://www.mazda6tech.com/index.php?option=content&task=view&id=47&Itemid=