Alright here is what I'm trying to do. I'm trying to use the sed command to sort a field so it comes out like lastname firstname

so say if I have something like this

Bugs Bunny:603-479-5498:12/9/09/:20300

and I want it to come out like this

Bunny Bugs:603-479-5498:12/9/09/:20300

how would I do that using sed? Now I know that I could do it perhaps using awk, but please tell me how to do it with sed