Actually you don't require a WBO2. It all depends on what condition your stock one is in. A lot of people have the stock narrowband O2 sensor right in line with their WBO2. Mine is as close to dead on as you can get. But the WB helps. MPNick is the only one who sells them, no more vendors, so other then a used one, you will have to go through MPNick. And IMO, is the best way because you get all the support you want from him. He will still give you support if you get a used one, but he wont go out of his way like he does on new sales. But the forum can give all you would need also. I've been running it since the beginning so I know it pretty well. There are a bunch of other people that know it very well also, so support should not be an issue.
Tuning is simple once you get the hang of it. Add numbers for fuel, take numbers away for less fuel. The trickiest part is tuning the switch point, but that is even easier now with the newer turbo modules.(thumb)