Now I remember how we didn't conclude anything on the warranty thing before.

Let's assume that the prohibition of outside service is not there until someone actually reads it.
Assumming that I bring my own oil, filter, ring, etc, do most oil change places (such as Jiffy Lube) have the tools (wrench, etc.) to do an oil change on the Boxster? This may not be a bad idea, as I can probably find such a place closer to my storage and the drive will be shorter before I store the car with the new oil. Of course, if I do it I'll be standing right there watching like a hawk.
Z.