If your truck is not lifted get the hd shock. I've been happy with monroe in
snow plowing applications. Although I have not plowed snow with a 1/2 ton
truck.

How much plow weight are you carrying. Make and model

Nothing much to it.  The bottom bolt is accessed from the front - it's got a
flag nut on the back (a flag nut is a nut pressed in to a piece of metal
that jams itself against something, preventing the nut from turning when you
loosen/tighten).   Once that bolt is removed, remove the shock tower from
the top by removing the three nuts holding it down.  Depending on the
clearance, you can sometimes pull the whole shock still attached to the
tower up and out.  If not, remove the top shock nut (hold the stud on the
shock from moving with a wrench or vise grips.  Better shocks have an allen
head broached in the top of the stud for this purpose), remove the tower,
then pull the shock out.  On a relatively new/non-rusty vehicle, it's pretty
easy.

On an old rusty shock, it can be a bitch to get the top nut off.  If you can
fit a Sawzall in, you can cut it off.  If not, you could split the nut with
a cold chisel.  On some shocks, I've resorted to griding a couple of flat on
the rod with a grinder, then grabbing it with a set of vise grips to keep it
from turning - but in your application, the coil springs would be in the
way.

If there's enough threads showing on the stud, you could double-nut the top
of the stud (jam two nuts against each other), hold the top nut, and turn
the one that's holding the shock to the tower.

Sometimes you have to get a little creative.

Of course, before resorting to the above methods, soak the nuts with
penetrating oil (real penetrating oil, like Kroil or PB Blaster.  WD-40 is
not that good of a penetrating oil) first.