Nice , yes remove (backup first on pc) also old gmapprom.gma files and gmapprom.unl files from nuvi or your map will result locked.
Replace old files with the new ones, look at garmindevice.xml for the right paths.
See this thread for reference:
[Only registered and activated users can see links. ]
After that run Webupdater, probably if it's old, it needs to update some files like voices, traffic.txt etc