I agree 100% with USMCFLYR (especially since he's quoting the book).

Unless other means are specified on the IAP, in an NOTAM, or verbally by ATC, you need all required navaids. ATC might be able to give you an alternate missed, but they probably can't just waive a required navaid otherwise.

You can only use GPS where published.

This applies to not only the obvious primary navaids but also to missed navaids and things like cross-radials which do not have a published alternate means. Would not apply to a step-down cross-radial on the non-precision if you are doing the ILS, only what's required for the procedure you execute.