A windowsill might be enough as long as it is cold.
The plan should exhibit no signs of growth during this period of time, if it does, it's not truly dormant.
Also, it is not neccessary to put the plant down the first year you own it. Chances are it's only been out of tissue culture for a few months if you just bought it from the store, and you can probably get buy just growing it straight through till next thanks giving... however, it's growth will be better if provided with dormancy.
and spraying it down with fungicide is an excellent idea.