The thing is that if you have been hacked, and you're not absolutely positive 
what might have been changed, you run the chance of executing some command in 
the future that re-opens the back door.

Unless you run something like Tripwire that will tell you exactly what files 
were changed, you're better off with a wiped disk and a reinstall.

(I know you built a new server in this case, so when you're done playing with 
the hacked box just be sure to snuff it.)