Can the Lord change someone who has been steeped in religion their whole life?
Yes. The Lord can change a person steeped in religion their whole life. The context describes a woman who had been in church all her life, found no satisfaction or joy, and feared God was not satisfied with her. When she believed salvation is by faith plus nothing, her life changed, bringing freedom and joy.
Les explains that he received a letter from a lady who had been in church all her life, yet never got any satisfaction, never had any joy, and was always afraid God was not satisfied with her. While listening to teaching back in Romans, she came to believe that it is by faith plus nothing. Les says that all of a sudden a change came over her whole life, bringing freedom and joy. He says it is thrilling that the Lord is able to do that with someone who has been so steeped in a religion of one sort or another. The same grace message continues in Galatians: we are not under Law but under Grace.