Open an existing RSLogix500 project, and go to Tools > Database > ASCII Export > then go to the CSV tab and create a csv file.
Then open the csv file with Excel, and you can see the structure that RSLogix 500 uses for import.
Open your autocad spreadsheet side by side, and copy and paste the portions you want into the csv file.
You can delete stuff that you don't need to mess with like the S status file comments and such.
When you have the file populated with the data you want, you can then import it back into RSLogix. It will replace the comments that you have edited with whatever is in your csv file.
Note that the comments database for address is broken into several fields. The first one is the symbol field. All symbols in RSLogix must be unique. The next 5 columns represent the 5 lines in the address comment. By default, RSLogix allows 20 characters per line, so you may need to edit the descriptions to conform to this limit, or they'll get truncated.
I like to display the entire worksheet with the font "Courier New" which is a fixed width font. You can then adjust the column width and easily see when you are running out of characters in a cell.
This should get you started...