The bearing retainer can be removed easily and the gasket and orings replaced. Installing the seal is best done with a socket that fits just inside the steel outer shell, and pressing it in with a vice.
The front bearing might be removed if you have the specialized puller that draws the inner race between the balls. I doubt you'll have that. Installing a new bearing will be impossible. If you allow the input shaft to slide forward while changing the seal on the bearing retainer a synchronizer shift plate may become dislodged, and you'll be dismantling the entire trans to assemble that one again.
Throw away the socket head bolts, get some 7/16 capscrews of the same length, and install the bell housing first, then the trans. Just why Volvo used those socket head bolts is a continuing mystery, and they are not needed.