Whomever was in charge of designing the stock Toyota trunk shocks probably did not take into account that they would one day have to be replaced. The way they are designed they are very difficult to remove. The two bolts at the bottom of the trunk shock are no problem. It's the ballstud-bolt at the top that takes work getting out. The screw is thread-locked in using locktite or some other screw adhesive. This means it is nearly impossible to remove (you will strip the bolt trying) unless you first apply direct heat to the bolt. I will get to that later on. In addition, the ballstud-bolt is made out of a cheap pot-metal that easily bends and strips. This is why I recommend cutting through the ball stud and then using a socket wrench to remove the bolt. You are much less likely to strip the bolt torquing it with a socket wrench from six sides of the bolt rather than only two sides from a hard to reach angle with pliers or a wrench.
Oh and don't try and take both trunk shocks off at once. As you will see for yourself the trunk is quite heavy even with just one trunk shock off. Remove and replace the trunk shocks one at a time, otherwise you may end up with a trunk smashed on your head or hands.
Are you getting tired of having your front or rear trunk lids fall on your head? It's probably time to replace your hood shocks. These are among the most disposable of parts on the Boxster. They will fail - it's just a matter of when. Replacing them is an easy task, however one that is made easier with small hands that manipulate tiny pieces. With a little bit of patience, you can replace your hood and trunk lid shocks in about 30 minutes.