First, break it. Doesn't matter how. Being drunk helps. You won't remember the details and until confronted with the reality, you'll think it was a weird dream.
Don't replace it right away. There are more important things: brunches to attend, commas to delete, Say Yes to the Dress to watch. The detached lid is as cumbersome as a Novocaine-injected tongue, always in the way, but you put up with it. You even get used to the wobbliness after a couple of days. But upcoming house guests are a good motivator to fix it.
There two options: Call the landlord or do it yourself. The landlord is a nice guy, but you have a feeling that he worries about you a bit, the building's token Single Lady. Mr. Roeper also has a tendency of not saying when he's dropping by and you'd rather not hear him buzzing your door while stepping out of the shower. It wouldn't be the first time.
Plus, when you mention to your most handy-dandiest friend that it broke, in an off-handed way loaded with meaning, he replied "That's really easy to fix."
At Target, when the redshirt asks what size you need, say "Toilet-sized." When he doesn't laugh, just pick one, any one, then take it and your dumb joke home.
Start unscrewing the nuts holding the bolt part of the seat in place. A wrench would be helpful, but you probably don't have one. We evolved to have five fingers for several reasons and here is one of them. Your mind will wander as your fingers move in circles.
You can't remember your parents ever replacing toilet seats. If they did it, it must have been at night, when they did other secret adult stuff that you had to learn on your own, like filing taxes and walking in heels. Or you may have been too busy watching cartoons (a possibility). In college, one of the maintenance crew fixed a broken seat in your dorm bathroom. He teased you for your 12-inch TV and the next week knocked on your door with a massive television he found nestled next to the dumpster. It was constructed during Reagan's presidency and still worked. Even though you can picture him- a bald Paul Bunyan with a hearty laugh who loved to tell dirty jokes- you can't remember his name. This makes you sad.
Quite some time will have passed with minimal progress. Frustration grows.
Enter the wishing stage. Wish you hadn't broken it. Wish you were sitting anywhere but this dusty bathroom floor. Wish you weren't sweating. Wish you weren't so proud. Wish you weren't alone. Wish you hadn't wished that. Wish wish wish wish. Turn turn turn turn.
Stop. Realize the entire time, you have been turning the screws the wrong way. The plastic is warped, but you can pull out the old seat, fit the new one in through the holes, and a minute or two later, the new seat is screwed into place, as if it was always there.
Stand up. Open the lid. Shut the lid. Open it, shut it. Wash your hands, please.
Have a beer, have a glass of cheap wine, have a tumbler of melting ice and sharp gin. Even a plastic mug of Kool-Aid will work in a pinch. The most important part is to stand a little taller.
(Thanks to the How-To Issue for the inspiration.)