I recently did this and the instructions posted by Ho
are what I did (except I did not remove the taillight
housing -- that might have made it easier). I did make
the mistake of unbolting two bolts that hold the "ball"
bracket that the front end of the strut connects to. Don't
do that, you just have to really pry at the shock end to get
them off.

I did notice that the wiring that passes through the drivers
side hinge of the tailgate had the insulating tape worn off.
Since I had it all apart I took the opportunity to re-wrap
the wiring. Might be something to check.

I'd also recommend a helper over a 2x4 for holding up the
gate since it helps if they push up the tailgate just an
extra bit while trying to snap in the new shock.