LOL...awesome Thats the cool thing about buying stuff for your vehicles...
If you buy a big screen TV or a PS3, its right there for her to see.
But if you put it in your truck, she would never know even if she was looking directly inside the engine bay

 

I ordered headers and had them sent to my neighbors house. Then I bought a cam and brought that over there. I eventually told her about the headers and when she showed up while the cam swap was being done, I just told her it was headers we were putting in. She don't even know what headers are or what they do!!!

You need to start thinking with your dip stick!!