I'm assuming that you have some CAD plans and that you'd like to "restart" the project in Revit, is that right? If so, the best practice is to link the CAD files (not attach) into the corresponding Revit view and use it as a guide for "tracing" your Revit walls/floors/etc. on top of. When you're done, just remove the link and you're CAD-free.
If you have some sections/details in CAD already, there's no way to directly convert those into "live" details. Although if they're standard details and unlikely to change, there's really no reason you can't link or attach them to drafting views that are referenced from your model. However, I would caution that this is a last-minute, short-term solution, while the better solution is to re-draw the details natively in Revit.
Hope that helps.
Ross Kirby
Principal
Dynamik Design
www.dynamikdesign.com