Do you mean you can't wire the RemoveDuplicates sub-VI, or are you wanting to use the entire 3D surface VI as a sub-VI of another VI?
If the former, you may have to rewire the sub-VI after it is replaced, depending on the terminal configuration of the VI being replaced. More details are needed to help.
If the latter, a few changes will have to be made. Most notably, the connector pane needs to be set up. Along with this, however, some things may need changing in terms of controls / indicators. The file path would probably work better as a control, so the calling VI can pass information to this VI as to where to find the Excel file. Also, if the files used are going to be changing size, the Cell Range values will have to be changed. Finally, the way the 3D surface is displayed would have to be changed in some way in order to update the Front Panel of the calling VI.
I'll try and help with anything you have questions about, although I will be leaving the office rather soon today, and won't be back 'til Monday.
-Cory