You can use all of the same editing techniques you would use in AutoCAD.
You might also try running Feature Recognition.
Can you attach the file here?
Any chance you have access to Inventor? If so, import it into Inventor then call the Inventor part up in Solidworks. As long as the versions are comparible.
You could also post the Autocad file here. I have a version of Inventor that I might be able to give you a better model to work with.