Getting the fan will ensure a well mixed air sample even during the most stagnant/calm conditions which helps. Most of the time, an un-aspirated shielded temp sensor is adequate. If you can keep the shielded sensor in a ventilated area in the shade, the fan should not be needed.
You will also need the Weather Link datalogger/interface/software package to use the VP with WD (or any other software).
I have 2 wireless VP systems, one with a repeater. I have certainly had periods of frustration with the wireless links, many external factors can affect the wireless performance and I would not rely on getting anywhere close to the max range that Davis suggests. For my locations it would be a real pain to run wire for either station, if wiring was really not a problem then I would be tempted to go wired.
Davis customer service is first rate. Is their stuff expensive, yes. Is it worth the price, it is to me. Are there cheaper alternatives, yes. Do they perform as well as Davis, probably not, but the difference may not be important to you.