E36 rear is easy. Just like you said. You may have to have someone stand on the hub to get enough droop to get a new stock coil in. Aftermarket/stiffer ones are shorter and just drop in.
The stock fronts are under very little preload. Not that I would recommend such a crazy unsafe thing on the interwebz but on more than one occasion we've just put a towel around the top of the strut and impacted the nut off.
IIRC only about an inch of preload on E30 & E36 so no drama. But again, I wouldn't recommend those sort of things on the internet
If enjoy really driving the car, good time to go to aftermarket springs. Can prob find a used set for cheap.