BMW E46 Rear Shock Replacement - 1998-2006 3 Series - All Models ↗
Rear shock swap shown on a 325Ci: support the lower wishbone with a jack, reach the two 13 mm top-mount nuts (under plugs in the top well on convertibles, behind the trunk trim on coupes/sedans), then the lower bolt.
Tools mentioned: 13 mm socket, trim tools, floor jack and stands
Written for all E46s; check the correct shock for M3/xi before ordering.