Apparently the bolt was changed from an 8mm hex (allen) sometime during production so it's worth a look at yours before any special tool purchase.

The strut isn't all that hard to replace if you line the two mounting holes, mount the forward bolt first, and maybe have help to raise the hatch as much as possible in order to get the rear mount flange under the hinge arm.

Sometimes one strut will give a nice gentle action to the hatch and it will stay wherever you like. When both are new watch out for an uppercut, especially if you have a glass jaw.

There are at least five other threads on this topic that come up in a simple search.....