Arduino and PLC RS232 Communication Using GSM shield

I have Siemens Step5 PLC in another country, i Want to open Step5 Program on my computer and make online PLC connection and download certain program on PLC i want to use arduino uno+ gsmshield on PLC side and Communicate with arduino uno + gsmshield on another side,,,, How can i make this project in detail.

So there's no internet connection at the remote site? That's tough.

I would prefer to just send a person out to the site with instructions on how to download the file. Is it impossible to have a person do that?

I'm sure Siemens has a solution if you have internet or a GSM phone with an internet connection. It probably costs a lot, but how much is this remote site worth anyway?

Does the remote device have to be Step5 or can you use the Arduino to do that job?