It's pretty easy, but before you start make a backup of your library (file>library>backup). That way if all goes horribly wrong you can move the files back to their original location and restore the library.
Once you've moved all of your files to the new location, open rekordbox and go to "File>Display All Missing Files". Here you can select all missing files by using command+a and then click "locate"... Depending on how many files are missing you may not want to select all files at once, instead select smaller blocks to relocate bits at a time. At the top of the window that pops up after you click "locate" will be the name of the first track that rekordbox is trying to find. You need to find that exact file yourself by browsing to it in the new location (where ever you moved it to on your hard drive) and click "Open". Rekorbox missing file manager will then ask you if you want it to find other missing files using the location of the track you just selected. Click "Yes" and all other missing files (that you originally selected) will be located. All of your cue points, playlist and analysis info will be just as it was before.
If I was relocating my entire library like you are I would probably move them to the new location without changing the structure of the files/folders within the "Music Folder". Just a guess, but this may make it easier/quicker for rekordbox to relocate them.
If you're nervous about it, don't move all the files/folders at once, just move a few and test the process out first for yourself.
