This situation that you observe only exists with PADS Standard (netlist) projects at this time. PADS Standard Plus (integrated flow) displays the new Replace Part command and triggers the wizard panel you are interested in examining. Let me know if you want to explore this feature using an integrated flow database as one is provided in your VX2 installation.
Why this feature is not available in the netlist flow?
It was originally developed for the PADS Integrated project type (PADS Standard Plus) and Xpedition flows based on the architecture of the Central Library and the part mapping mechanism in these flows. The netlist flow (PADS Standard) uses a different mechanism to assign symbols into parts (gate/slot assignment). As yet we have not decided wether the effort required to modify the code to work with the netlist flow can be justified when considered with the other items that are currently under development.