Thanks everyone! That was easier than I thought it would be. Really.
I tried two things:
1) For Stairs - The sign was opposite of what I wanted. I took a copy of the texture into paint program. There was a flip image horizontal option. I did that but wording “Stairs” was backward. Ok no problem. I reversed, selected word “Stairs”, copied, flipped, pasted. Done. Put sign up, went into surfaces and changed. Easier than I thought.
2) For Custom Sign - I created a plane as suggested, and sized it. For the wording, I kind of cheated. I found an online street sign make. It had an official looking font that I liked. Background was green with white lettering and entire sign was outlined in white. Ok easy enough. I saved, took into paint. Grabbed the other sign, picked the color with color picker and changed green to blue. Saved and then merged the “sign” into my scene. Very pleased.
Actually all of this was very easy and fun. I had my doubts this morning though lol. But it was all pretty painless.