If you are after a GUI system, Genomics Workbench by CLC Bio Ltd is the easiest for a complete novice to get into. It is something of a "black box" in terms of assembly though, but I'd certainly recommend it to get up and running quickly - if you then decide to switch to more traditional assemblers like SOAPdenovo or Abyss then at least you've got some work done and the postdoc will have more of the required background knowledge.
The command line interface is a bit of a scary screen if you are not that used to it at first. In your experience SOAP is a good option then, thank you!
If there would be a step by step tutorial laying around, where would be a safe place to look for it first?