Does the Bible tell Christians to practice a system of worship in the age of grace?

Les explains that the book says nothing about practicing a system of worship in this age of grace, because Christ nailed all that to His cross and we are now free. He points to Romans 13, where Paul says not to regard one day higher than another but to regard every day alike. Les notes he has nothing against Sunday, but even Sunday is not taught in Scripture as a special holy day above the other six days. Paul merely said that as believers come together and bring their offerings on the first day of the week, resurrection day, that is acceptable. For the believer every day is alike, and we are to serve God just as much Monday through Friday as Saturday and Sunday. Les also connects this to Galatians 4, where Paul wrote because Judaizers were convincing Gentiles they had to keep the Law if they wanted salvation. Paul admonished them not to fall under the temptation to become legalists, warning that legalism appeals to human ego, but God will have none of it.