Hi Bill,
You might find Chris' simple answer on when to use 'y' and 'en' useful -
As for when to use the direct object pronoun 'le' or the indirect object pronoun 'lui', you will need to study the following lessons -
Using lui/leur = him or her/them (French Indirect Object Pronouns)
Using le/la/l'/les = it/him/her/them (French Direct Object Pronouns)
Hope this is helpful!