I think your confussing two different types of trading. Trading for other DVC resorts at the 7 month window is not usually that hard though it can be at times. If you want WDW, you should be able to get something. If you want BW at Xmas, you are likely out of luck.
As for exchanging through II, it's another matter. You should search AT LEAST 1 year out and be prepared to wait for several months and maybe longer. Remember someone esle has to give up a unit before it's available and that there may be others waiting and some of these may have higher priority than you (like Marriott to Marriott). Be realistic, it's not like a hotel reservation.
Lesson number one in timesharing, IF IT'S NOT WRITTEN DOWN, IT'S NOT APPLICABLE. Of course your guide made it sound too good to be true. DVC will have very good trade power but it's not the only resort to do so. You can likely do best with direct exchanges but while your looking for a direct exchange, you can let DVC be looking for something also.
Good luck.