We're fans of The Little Seedling (formerly Tree City Diapers). Their website is treecitydiapers.com.
They have a big selection of slings to try on with a weighted baby (or your real baby!) and will help as much as needed with the mechanics of sling use.
Also, another good (maybe even better) option is the Ann Arbor Babywearer's meeting. Each Tuesday, the group meets at Briarwood Mall's playspace from 10a-12p, and the leaders keep a huuuuge library of different types of carriers/slings for folks to try and borrow for a couple of weeks so you can see what works and what doesn't before you buy. We love it!
Hope you find something that you love.