The external wireless probes are the trickiest bit, imo. If you wanted to interface to commercial wireless sensors you need the smarts to implement your own receiver hardware and software, or find somebody else who has done it for you. It's possible, but hardly suitable for your first project. If you have the option of putting an Arduino at the remote sensor using a radio link back to another Arduino doing the control stuff you have a solution that would be easier to design, but then you need to package and power the remote Arduino. Depending on your situation that might be quite hard.