rebuilding a system remotely?

[Miles Fidelman <mfidelman@meetinghouse.net>]

Hi Folks,

I have two machines sitting in a data center.  One of them, I've just 
finished, very carefully, configuring for production use.

The other machine I've used a bit as a sandbox for trying things before 
doing them on the production machine - and at this point the sandbox is 
pretty well messed up.

I'd like to either
a. rebuild from scratch to Sarge
b. upgrade to a clean testing release.
either way, without a trip to the datacenter to rebuild from a CD.

So... is there some easy way to do a remote rebuild of a machine that 
already has a (still) reasonably functioning base system on it?

Thanks for any advice,

Miles Fidelman