Late February until mid April. Our season has been extended this year from March 31 to the end of spring break, usually the first week in April. Best time to get on good numbers of big fish. Of course, the weather is the king. If forecasts hold, it will be a more normal winter. Ice should be good.
As for guides, quite a few up here. I can message you a bunch of names. As for accommodations, they book up quick. Most American groups book the next year before they leave. South beach casino, canalta hotels in Selkirk, or in a pinch right in Winnipeg.