Og det åpnet opp øynene mine!
'skiltet' doesn't have any other meanings than a thin plate of metal with text. What you're thinking of would be 'tegnet' in Norwegian.
When this song first came out, I was young enough that I didn't understand the word "sign" to have any other meaning than this. So, I still always think of this song as being about a road sign that was really enlightening.