FWIW, here's how I did it. Proceed with due caution. The weight of the car must be on the jack supporting the control arm. This keeps the spring compressed while the top nut is off.

Remove wheel, support control arm with jack so that spring is contained after you remove nut at shock tower. Hold shock piston with 8mm allen while you undo the top nut. Remove three nuts holding strut mount. Compress piston, slip new boot over shock, swap new mount for old. Attach shock mount with new nuts, 20nm. Release piston, hold piston again with allen while you tighten nut, 60nm. Reach up and attach rubber boot to ears on bottom of shock mount. Try a dry fit when you get the parts to see how the boot attaches.

glenmore
1991 300CE
2000 C280