Yes the two bolts at the bottom and along with the top one have to be loosened to adjust your chain,the two that face towards the back do the chain tightening though.
As far as that white dohickey behind the sprocket,it hold something in place in the tranny just can't think what it is at the moment,I'm having a seniors moment.
If it has a chain case saver on it ,it would wrap around the front half of your sprocket to fill in the space between the sprocket and the case!!!
Those axle bearings can be a bit@* to get out.a good hunk of brass or hard wood will be needed to whale the axle out,then you got to get the bearings out of the housing,I used a long punch and tapped them out,you will know what to use when you get that far.