Elec. Problems? 4 quick horn honks, airbag light

Hi all, I do believe I've got some electrical issues and want to exhaust all my resources before dropping it off at the dealership.

2005 PreRunner SR5, airbag light has been on at least a year (dumb, I know), and now occasionally while driving I'll get 4 quick honks of the horn randomly going off. A couple times that its occurred, I'll notice the dash lights flash on and off as well. And then just yesterday, while passing a friend out biking, I realized that when I went to honk the horn normally, it didn't work. Any ideas on things I--with little to no knowledge of my vehicle's electrical system--could check and/or attempt to repair?

Secondly, if this is something better attempted by a professional with diagnostic machines, is there an alternative to taking it to the dealer for them to charge me $100 just to hook up to their computers? Do non-dealers have similar diagnostic computers? Any recommendations on shops in the Fort Worth, TX area?

Thanks!

 

*bump

Anybody...?