Catholicism: Is Sunday Observance Necessary for Salvation?

For Catholics, is Sunday observance necessary for salvation? Is Sunday observed in the same way as the Sabbath was observed, or is there a difference? Additionally, what about the observance of the day and the Eucharist? Is it mandatory to attend Mass *and* receive the Eucharist? If possible, I would like to know about Catholic documents or catechisms that define this. Thank you!