for the ground, there's a bolt that has a nut attached to it at the top left area of the fuse box. use that. get either a ring style or spade style crimp-on wire terminal and attach it to the negative wire, then secure the terminal behind the nut along the bolt, such that the terminal is making good contact to the metal and is held tightly into place by the nut.

what you did for the airbag sounds about right.