No find/replace in the stock tool though. I use Paul Hormis' renamer script instead... http://www.hyperent.com/TiM-Scripts-UI.html Naming along with selection sets/layers is the best organization for me.
blurs object script definitely has the handiest object management/naming toolset. For bipeds though, it already has that built in. Go to motion panel>Biped tab>click on "modes and Display" bar>Name: text field use that and just change the name and it changes it from Bip01xxxxx to whatever you want.