Rebuilding the timing cover

I am in the process of rebuilding my engine and while my initial thought was "if it ain't broke..." I have since graduated to the "as long as i have it apart" philosophy. At present it's the timing drive cover. I am curious about the drive seals, is it preferable to leave them at the edge of the pocket or should they be pressed up against the c-ring, does it matter ?

Any suggestion on the best way to press the cam drive shaft into the drive bearing.

One more question for the moment, I have read as many of the posts as I can find regarding the timing cover rebuild and I do not understand why the position of the timing gears relative to the crank gear makes any difference. I see that some very smart people mark the sprockets and others, as I, think that its only the cam and flywheel marks that matter.