Not without some heavy modding. Dell uses proprietary front panel, USB, and other connectors (like the power button) making such a change very difficult. You would also have to (likely) change the PSU as Dell's are often very underpowered.
Your best bet would to either just upgrade to a new case and then build your new system - or find another Dell motherboard that supports the processor of your choice.
There are several sources (a very good one is http://www.txcesssurplus.com/)that
sell Dell components and there is eBay. Good luck