Ah, ok, I just re-read your original post. Are you wanting to use the data in the MER file to restore the descriptions and such in the RSS file?
You can definitely import/export to/from RSLogix. Go to Tools -> Database -> ASCII Export to export the existing database so you can see the format. Be aware that descriptions are broken up into fields 20 characters long. If your descriptions to be imported are longer than 20 characters, you will have to break them up as well or it will just import the first 20 characters. It's been a long time since I had to import into RSLogix 500, but I used to have a spreadsheet that had a macro to break up the longer descriptions.
In View Studio for ME, go to Tools -> Tag Import and Export Wizard...
Then you pick "Export...", project type, the view studio project and destination file. It'll export the tags to a CSV file. Be aware, though, that it isn't necessary to use tags in View Studio. It's entirely possible to do the entire project without using any tags at all. The PLC connections would be embedded directly into the display objects. Your tag export won't include any of that. Or you could mix the two methods and use tags and direct connections.
If you export the displays to XML files, you can open up the XML files and see the "connection name" fields. That may help you see where stuff from the PLC is used.
Once you have both formats, you should be able to transfer one to the other. If it's big enough, you could probably write a macro to do the conversion automatically. Then you can go back to RSLogix, Tools -> Database -> ASCII Import to import the new descriptions. Of course, I would work with a copy of the RSS file, just to be safe.