I have one concern and that is that your original wallet was not a Neoscrypt wallet - it was pure scrypt back then. So we can try and see if this works.
1) Go to https://github.com/guncoin/guncoin/releases/tag/v1.3.1.0 and download the Windows self-extracting file.
2) Backup your wallet.data file in your Users/App Data Guncoin directly (not necessary, but generally a good idea)
3) Run the windows exe file. The wallet will load and then will have to resync with the network. Your coins should show up there.
Running the new wallet should sync with the old coins no problem!!
Backing up beforehand is always smart though.
Another way to back your coins up is to manually create a paper wallet by going into your help menu and select the debug window option and then the console tab.... On the command line of the console, type the command 'dumpprivkey' then your wallet address then you will see a private key generate... Copy both lines of your private key and wallet address and then repaste it in a Wallet.docx file and also physically print it out and there you have it, your paper wallet... No need to goto to a dubious website... Assuming you've lost your backed up Wallet.dat file or your hardrive has crashed or files were erase you can load back your paper wallet into the network by simply going back to the console window and type in 'importprivkey' then cut and paste your private key address from your Wallet.docx file or manually type each Numeric Letter directly from your physical printed saved paper wallet (pain in the ass ) and your coins should appear once again.