OT and New Testament Sabbath (2)

Since the priesthood changed from the order of Aaron to the order of Melchizedek, what else changed? In Hebrews 7:12, it reads, For when there is a change of the priesthood, there must also be a change of the law. As we can see, something changed not abolished. When we can think about the word "order" as in the order of Melchizedek, what does it signify? Basically, the way or manner it which something was kept from the Old Testament to the New Testament. In order to understand the change, we need to understand how it changed from the Old Testament to the New Testament. Then, in order to understand how Sabbath is kept in accordance with the example that Jesus Christ taught us, we need to understand how it was kept in the Old Testament.
In Exodus 31:12-13, it reads, Then the Lord said to Moses, Say to the Israelites, you must observe my Sabbaths. This will be a sign between you and Me for the generations to come, so you may know that I am the Lord, who makes you holy. At this time, Jehovah God gave the Israelites a command. God did not suggest or ask for them to observe His Sabbaths but He said you Must observe Sabbaths. Why? By keeping God's Sabbaths we get a sign between God and us. Recalling God's messsage in Genesis 2:1-3, God promised rest, blessings and holiness on the 7th Sabbath (Saturday). How amazing because we also realize that God also promised a sign between us and Him by observing the Sabbath. God acknowledges us on the Sabbath day! If we continue in verses 14-15, it reads, Observe the Sabbath becuase it is holy to you. Anyone who desecrates it must be put to death;whoever does any work on that day must be cut off from His people. For six days, work is to be done, but the seventh day is a Sabbath of rest, holy to the Lord. Whoever does any work on the Sabbath day must be put to death. In verse 14, anyone who desecrates the Sabbath, is put to death. In verse 15, whoever works on the Sabbath day is put to death. Hence, to desecrate the Sabbath is to work on the Sabbath. However, what is work? If I move a pencil from one end of the table to the other end, is that what God considers work? Although it does not require a lot of effort, we need to understand and accept God's viewpoint on what work is.