Try moving the steering wheel to take pressure off the key. The wiggle while you slightly try to pull the key out. If those don't work then you are going to have to let the key stay stuck there until you can replace the switch itself. However, as you have discovered, the electrical components are on with the key in the ignition. So you need to get home, pop the front trunk lid and disconnect the battery until you can replace the switch! And don't shut the trunk!
This is a common problem with Boxsters. It is the exception rather than the rule to the entire housing to have to be replaced. 99% of the time it is only the switch itself, and it can be bought from any Audi dealer for less than $30 to $40. It is Audi part # 4A0 905 849 B.
It is an easy DIY, except that you have to be nimble and be able to do contortionist tricks to get into the proper position under the dash.
There is an excellent write up at this link with detailed photos:
Porsche Boxster Ignition Switch Replacement
Threaded Mode
