Changing plugs on an E36 six is straightforward once the coils are off. On the M50/M52/S52 each cylinder has its own coil:
- I unclip the coil connectors (release the wire clips, don't yank the wires), unbolt the coils and lift them out.
- I reach the plugs down the wells with a 5/8" (16mm) spark-plug socket and a long extension.
- Fit the correct plugs and check the gap — commonly around 0.8mm / .032" on the M52 family — if they aren't pre-gapped.
- Torque to roughly 23-30 Nm (about 20 ft-lb) — snug, not gorilla-tight — and I put a touch of anti-seize on the threads; cheap insurance in an aluminium head.
Interval is every 30,000-60,000 miles depending on plug type. If you're chasing a misfire, the plugs and coils are the first, cheapest things I swap between cylinders to find the culprit Common Codes. The four-cylinder M42/M44 is the same idea with its own coil arrangement.
For this you'll want the correct plugs (and coils if one's tired) and a little anti-seize — I've put them below.