Serial Server with SM5100B

Hey, I have a serial rs232 device in a car, and i now have specific windows software i use to connect to the device, and read/write data. I have been asked to design a GSM based system to bypass the need to use the serial cable each time we want to read from the car. I originally thought about using a GSM modem, but had little luck. I have since moved to using an arduino with a SM5100B shield. My intention was to have a windows server running with a Serial Server running on the server, which can listen for TCP connections, and then turn them into virtual COM ports, so the proprietary software can run on the PC and not realize the COM port is actually remotely connected via GSM. I found this software, which i think will handle the COM port part...

I have the sm5100b working in a very simple fashion, sending SMS, receiving calls, etc... but, now i need to figure out how to make the arduino send all data from the serial port to the server, and all responses from the server back to the serial port, basically acting as a relay between the server and the serial device connected to the arduino.....oh ya, whats the best way to connect a serial device to the arduino? just pick two pins and use newsoftserial?

all the help is as always, much appreciated!