yep just tap the bearing all the way in, same with the seal. You might need a little grease or oil to help yua. nothing needs to go in the seal.
As far as that tube goes it's a spacer,i would grind the burrs of off it so it dont tear up the bearing.
get a long straigh screw driver and a hammer and hit the inside of the carrier where the old bearing and carrier meat. hit it then move around and hit it again untill it comes out. the seal, just pry it out on the outside.
as far as the rear end sounds like u need new carrier bearings. and my friend has a yfz 450 and his ele. start gear kicks when he stalls it out so it just might be that.