fitting shock absorbers

Nugget

you dont have to remove wheel to fit the rear shocks,just put your jack under your diff,(jack up to a height where you can comfortably slid under your car)then place car stands under your chassis and let jack down slowly to rest on these stands and leave jack under your diff.this way you can adjust height of the car to fit new shocks.

it will be an easier job to do the front with the wheels off and repeat the last procedure only place the jack under the front end cause your diff will be offset,cheers.

No mate, Just undo the nuts.

You don't need to remove the wheels or jack up the vehicle. Just undo the nuts and fit the new ones as the old ones came off. Just remember not to tighten the new nuts too much, just enough for the nylon locnut to grab.

Barnesy

Depends a little on the shocks as well - some are very hard to compress so you may have to jack the car to have the wheel off the ground and thereby maximise extension.

If they are hard to compress you can use a strap or another jack underneath to help.

As has been said before you can do the job with the car on the ground however sometimes removing the wheel allows better access.
Usually the nuts are difficult to remove from the old shocks, they are usually tightened to about 55 ft lbs.
One thing to be aware of: if you are fitting gas filled shocks hold them in an upright position when squeezing them in to locate them in position. If you don't do this ie if you hold them horizontal then you can induce gas past the valve which can cause a free spot at the top of the stroke. If this happens you will need to press them up and down a few times while holding them upright to bleed them.
Best regards Cruiser