auxilary

get spring compressors, first of all. never ever do springs with belts or ghetto methods. I recommend doing shocks at the same time you're doing springs, since you'll already have the struts out. going from memory here, hope it helps

front:

removal:

-disconnect sway bar endlinks
-remove the 3 nuts on each strut (do not remove strut nut in the middle of the isolator! barely break it loose, but do not remove it)
-pull the assembly down so it sticks down past the fender.
-if this is not possible, unbolt the 2 bolts holding the balljoint to the strut housing.
-remove and position assembly carefully, because the brake lines are still attached.
-apply spring compressors .
-remove strut nut and isolator. don't loose the strut bearing and perch
-remove spring, and slowly loosen the compressors to get them off.

install:

-lightly compress new spring with compressors, put it on the strut perch
-clean and regrease the strut bearing, it'll make turning so much easier
-put upper perch, new bump stop and dust boot on the strut, tighten the strut isolator nut to spec (refer to haynes/chiltons/fsm)
-reinstall assembly, tighten 3 nuts on top with bolts (25 ft lbs if memory serves)
-attach balljoint and bolts (50 or 60 ft lbs?)
-put sway endlinks back in (15-20 ft lbs)

rear: removal is almost the same as the front, rear control arm has more flexibility so you don't have to take it out.

before you do this, I have a very good suggestion for you. Find some 240z isolators, they're 3/4" shorter than the 280z ones, and this is a nice cheap method of lowering your Z without killing the suspension travel!

theramz

If you are installing lowering springs, they are shorter and you won't need the spring compressor to put them in. Dangerous not to use them for removing the old springs. I did this in a junk yard and the isolator flew about 20 feet even though I had my foot on the spring. Good idea to put in new shocks at this time.

Bleach

Do the 240Z isolators work on a 280ZX?

auxilary

no idea. You might want to take a trip to the junkyard and do a comparison on the junker cars.