airbag light

I took my 93 previa in b/c the engine light was on and had some work done. When I picked it up, the airbag light was on. I took it to the dealer and had a diagnostic test done and was told that the airbag controller needed to be replaced. My concern is: could the light have been triggered by the previous work? I don't know much about diagnostics: are the results 100% accurate and I should believe what I'm told?