Hi!
Although I went to a different university, I help out the Theta chapter at Madison and have numerous friends and family members who joined sororities and fraternities there, so I know a little bit but I think there are others on this board who may know more than I do.
Of course, no one can really tell you how hard it will be to get into a sorority since membership selection is private.
That said, Wisconsin is not typically a school where sophomores are automatically dismissed and I know several women who transferred and were able to find a home there.
From my experience, recs seem to be increasingly popular and in general they often serve as a nice introduction. They are optional but wouldn't hurt, and if you have the chance to secure one/some, I'd say go for it.
Here's a link to an article on what to wear, that also explains how the rounds work:
http://www.uwgreek.com/recruit/documents/WhattoWear.pdf
And here's a link to the go greek website for information on how to register, etc.:
http://www.uwgreek.com/index.html