The model you have really will not serve as a replacement for the Digi One SP as it is a customizable product (-C part number). The plug and play version of the Digi Connect SP product would be a better fit (-S part number):
http://www.digi.com/products/serialservers/digiconnectsp#models
You might want to go back to where you purchased this to see if you can exchange it for the Digi One SP or the -S model of the Digi Connect SP.