Just to try and clarify things I have a couple of questions/comments.
Are you running Oracle Spatial or just the regular Oracle? If you implementation is just the regular Oracle, then you will only get tabular data back and not feature data.
In Author, you can load dwg files directly, but you have to remember that MG 6.5 came out prior to the Autodesk 2007 file format. I believe that 6.5 can read the 2004 file format. Change the default file save version in your Autocad Options to either 2004 or 2000 format and try again.
MG was not designed to directly show all attributes contained within source data files. Typically you have your dwg object with a 'key' field that references outside data sources (Oracle, for one.) Some background programming needs to be done then that when you click on the item a querry is made of the data source and then displayed in another portion of the browser window.
You really need to read the developer section of the documentation and talk with your reseller or the individual that implemented the server. Also consider looking at the content of the Mapguide discussion group on Autodesk's website. this url would be a start.