Motorola 3327? Are you sure thats your model? Don't see it on file with Motorola.
As for your question, not sure how to answer. The modem establishes the internet connection with your ISP, the router distributes that internet connection to the computers in your network. A modem with no router will still get one computer online, and a router with no modem will still network your computers together, they just won't be online. If your buying a new router, then yes, you will have to buy a new modem, or somehow set the modem/router combo to bridge/transparent mode. Have you thought about just buying a newer modem/router combo?