Well, as previous CFW's I highly doubt it will be a customized update as it's never been like that. You also should've already known not to upgrade if you wanted CFW installed. They've never gone from OFW to CFW directly. Even 3.60 needed Pandora so I bet 3.71CFW for the slim will also need Pandora.
Last is you should've waited and seen what was needed to install. You probably need 3.60 M33 installed first so I bet your SOL.