What are three specific lessons taught in Silas Marner by George Eliot, in detail?

One lesson in Silas Marner is that people are often accused unfairly simply because they are different. For example, Silas Marner has a "cataleptic fit" during church, and his friend William says, "to him, this trance looked more like a visitation of Satan than a proof of divine favour." William throws a suspicion of devilish behavior onto the innocent Silas. Silas is subsequently accused of stealing the church's funds, a crime he did not commit. William, Silas's friend, probably committed this crime but was able to blame it on Silas because Silas is marked as a bit odd but is, in actuality, a simple and good man.
The second lesson is that money alone does not make people happy. While Silas Marner turns to weaving and to hoarding the gold it brings him, he becomes less and less happy and more and more alone. Eliot writes of Silas in Chapter 5, "His gold, as he hung over it and saw it grow, gathered his power of loving together into a hard isolation like its own." In other words, as Silas accumulates more and more gold, he becomes further isolated from others. 
The third lesson is that love, rather than money, brings true happiness. Once Silas adopts the child Eppie, he becomes truly happy. In Chapter 14, Eliot writes:

"The gold had kept his thoughts in an ever-repeated circle, leading to nothing beyond itself; but Eppie was an object compacted of changes and hopes that forced his thoughts onward."

It is through loving and caring for Eppie that Silas discovers happiness and connection to other people and to the world beyond himself. The child is the true gold that Silas has long sought.