Hey,
Not sure exactly where in Manitoba you are, but have a look at the SAR Manatoba site and find the local team where you are. They should be able to fill you in on the specific on the pre-req, and recruitment process.
http://www.searchandrescuevolunteer.ca/
I can only speak to my group (Calgary).
Our pre-req are ICS100 (online/free like you said).
Our first aid req is for the first day of training. Worth getting in general, but you could put it off until you know you're accepted.
We facilitate police checks after you're accepted.
GSAR Basics is provided by us once accepted.
We run new recruit training over 4 evenings and 2 full weekends.
Any other questions?
/Edit: Short plug for a fundraiser we're running.
Steak night and Silent Auction
https://www.facebook.com/events/521358964717820/
June 4 - $25 (Kilkenny Pub)
Items include: Denver Broncos Payton Manning helmet with case, Calgary Flames signed Michael Ferland hockey stick, Calgary Flames signed Johnny Gaudreau jersey, hot air balloon ride, helicopter ride, and more