Technically, you can integrate any kind of transformation in Alfresco. This includes a transformation of Autocad files to viewable formats (PDF / SWF). I have had a few customers which used such an integration. But all of them were using a reasonably recent / up-to-date version of Alfresco, NOT Alfresco 3.0, which is more than 10 years old at this point.
Typically, such an integration involves configuring a transformer worker which executes a local binary via a child process (e.g. using a command line utility). Alternatively, there are transformation tools that would require you to implement some Java code to call a remote service (simple ReST or legacy SOAP). It all depends on what tool you pick for the actual transformation...
The file view in Alfresco is based on either SWF (older versions) or PDF, so you need to convert to PDF to view - or actually look into integrating a complex, custom viewer component that can natively display DWG files, which I have never seen / heard of.