I moved from PC to Mac recently and moved all my pictures and catalogue over, it was a pretty simple process. First though, BACK EVERYTHING UP!
There was already a folder named Pictures on tea Mac, so I first copied my folder structure from My Pictures on the PC to that folder.
My Lightroom Catalogue was in a Lightroom folder under My Pictures, but I can't recall if that's the default for Windows. If not you should be able to find it by searching for *.lrcat. I copied the catalogue into a new Lightroom folder within the Pictures folder on the Mac, but you can put it anywhere.
Then when opening Lightroom on the Mac, you can point it to location of the catalogue you have copied across and set it as the default in the preferences. If it has trouble finding any of your folders, you can right click on the folder name in the library module and point it to the new location, but as far as I recall I didn't need to do that.
Good luck!