galleypower,
The Canadian AIM states when referencing GPS Overlay Approaches;
"Unless required by the aircraft flight manual (AFM) or AFM Supplement, it is not necessary to monitor the underlying navigation aid, and it is even permissible to fly a GPS overlay approach when the underlying navigation aid is temporarily out of service. Nevertheless, good airmanship dictates that all available sources of information be monitored. "
The AIM also states that GPS overlay approaches are identified by including (GPS) or (GNSS) in the approach name i.e. (GPS) or (GNSS) NDB RWY 04.
Therefore, the answer to your question is yes and yes. You can fly this as a GPS overlay approach or a conventional approach or for that matter as a stand alone GPS approach based on the statement above.
best regards,
Bruce Waddington