Well i have to read the whole book if im to tell all changes so here are some:
Jeremiah 31: 31-34 foretold the change.
Hebrews 1: 1-2 change the direct-to-God interaction (like when God spoke to Moses, and other prophets) into a scenario where Jesus gets to meet them and travel with them instead (the case of the Apostles)
Hebrews 5: 1-10 tells about the change in priesthood. instead of assignment of several high priest, Jesus took the post. However, Jesus was not a descendent of Aaron and he was not even of the tribe of Levi.. (old testament tells that high priests only come form Levi's line) Rather, we find that the order of Aaron was not meant to be permanent (Hebrews 7:11). Hence, a change in the order implies there was a change in the Law (Hebrews 7:12-17).
There was a change in sacrifices (Hebrews 9:16-28; 10:1-8). The Old Law had yearly sacrifices for God to forgive us from sins, temporarily. The New Law had a single sacrifice that did free us from sin, the Crucifixion.