You won't be able to move it by hand. Those rods have enormous gas pressure inside. It is a good idea to replace them in pairs.
Open the trunk almost fully. Remove the rubber, sort of doughnut shaped buffers from each hinge (their purpose is to cushion the lid when it reaches its fully open position and only become visible when the trunk is nearly fully open). They just pull off sideways, towards the centreline of the car. Removing them allows the trunk lid to open a bit further making it easy to fit the rods without having to compress them. Jam the trunk lid in the fully open position using a stick, broom handle, etc, Unclip the old rod(s). Fit new rod(s). Make sure that the clips which hold the rods in place are securely attached. Replace the rubber buffers. Job done.