I took out one of the c-clips without the special tool but after replacing the bearing I can't figure out how to push the c-clip in. I'm kind of weary about jamming a flathead in my hand or damaging the center section. I guess my question is how much force should I use lol

 

Gotta use the tool to put that back in. No different than any other snap ring. They need to be very small. you can't force those in too much.