I've done it without any problems.
Best way to do it is to unzip the folder (which contains a VT folder and a readme) into a temporary location on your PC (i.e. My Docs)
In the RW directory (listed in the readme) make a copy of the GNER folder, and rename it to VT and then open it.
Go back to the location where you unzipped the download to, open the VT folder (in which you should find an identical file structure to what you have in the main RW folder) and copy the new folders, allowing it to overwrite any files/folders that exist in the ex GNER folder.
I've followed this approach myself and guided two friends through the same procedure and it has worked every time.
HTH and let us know if this sorts the problem
