...lead her father, Matsuno Rokuro Zaemon Nyudo, to attain Buddhahood.

Could someone please help? Thanks.

Your question is a metaphysical one, asking whether the teachings referred to could help one to attain a state of enlightenment, or simply put one on the path, to help on to move toward enlightenment. On the face of it, "to attain" is correct, assuming that the author asserts that Nyudo did in fact attain perfect enlightenment (a laughable concept).

Grammatically, "to attain" is correct if and only if Matsuno~ actually attained Buddhahood, which is a pretty dubious claim, to say the least. If it only inspired him to try to attain Buddhahood, "towards attaining" would be better.