Well...
1) You could just tell her? Honesty is the "best policy," right?
2) Find a cliff or canal...and report it stolen? While not the best policy...errr umm...ok that's a bad idea! We're just spitballing here; I have another idea.
3) Go buy a really nice couch (something you won't mind sleeping on for an extended period of time) and have it delivered to the house. Take it like man and sleep like a baby.
I'm actually with JEBIV on this one...I'd look into trading it in on a new one and let the detailers at the dealership worry about it. Unless your wife is like mine and wants a hand in all major purchases. Then she might feel slighted and pissed off for getting her a new car. Yeah. Or...maybe buy her a quad cab truck so you don't have to worry about this next time??
You could also call a few highly regarded detail places (even mobile ones) and get the whole car detailed...inside and OUT. But even then, it's still a gamble.
Cleaning a headliner is tricky because the fabric is very thin. Scrub too hard and it will show. Of course you could say: "Honey, it's something I wanted to do for you so you're driving a really clean car." Yeah she'll probably be really suspicious and expect it regularly from here on out. Hope that $25 Weber was worth the $300 detail. Money well spent. Alright, chop chop. The clock is ticking. You could also look into the cost of replacing the headliner...but that might take longer.
All of my BS aside...just tell her you F'ed up. She won't kill you. You'll probably get the grills in the divorce anyway.