Mower Gearbox Issue

Brought my leaking mower gearbox from the Bolens 1455 tractor over to my small engine guy yesterday and he showed me how to take it apart.  When we got into it, we found an oil seal on the bottom shaft (where the leak was coming from) had evidently been hammered into place, leaving it bowed in areas and helping to cause the oil leak.  We also found two shims on the bottom shaft.  However, the parts diagram shows a gasket and up to 10 shims can be placed on that shaft.  So it appears someone took out the old gasket but did not replace it.  The two shims by themselves may not be enough to prevent oil from leaking, especially under high pressure.  I called up Sam's Bolens, a reliable supplier in Indiana, and they had both shims and gaskets in stock.  I ordered nine shims and three gaskets, which I hope will be enough to deal with this gearbox as well as the gearbox on the rail-mower deck, and the spare gearbox.  Will have to schedule a session with the small-engine guy to put the 1455 gearbox back together and check the other two and fix them as well if required.  I wouldn't want a leak on the rail-mower deck gearbox to causing the gears to seize up and ruin the gearbox.  Prevention is better than cure, etc.  Hope to have all that done by 11/19, when Frank Glatzl is scheduled to come over for our next rail-mower work session.