Hey Kirby,
I weaned my daughter around 20 months and it took about one month. She did cry some, but it was always in my arms!
Also, my husband works late hours and is almost never available in the evenings, so I had to do it alone (some people have had success by having their husbands take over naptime and bedtime). Anyway, here you go:
Since your LO falls asleep at the breast, the first step is to wean her from falling asleep at the breast. I would recommend you start with her naps only.
Do your regular nap routine and then start breastfeeding. When she starts to slow down and show signs that she's sleepy, but not asleep, gently use your finger to separate her mouth from your breast. Expect her to cry, root around for it, and so on. If she's frantic, give it back to her and repeat. And repeat and repeat and repeat until she finally falls asleep without the boob in her mouth.
The first time you do this will be the longest and the hardest.
But once she's falling asleep at naptime without the breast, do the same thing at bedtime.
Then phase out the breast completely at nap time. Once that's done, phase it out at bedtime.
Some people do this gradually, some cold turkey. I decided to go cold turkey.
Yes, she cried and said, "nurse, mommy, nurse, mommy," but I held her, rocked her, and comforted her through it all. She fell asleep in my arms the first time after about 30 minutes. By the third day of doing this, she only asked to nurse once and then just cuddled in my arms until she fell asleep.
She's 2 1/2 years old and she now falls asleep with my just sitting in a chair next to her bed. She's a fantastic sleeper, by the way!
Good luck! M.