Yeah, you need those two tools. Keep in mind you also need the wrench that fits into the end of the spark plug tool. You can find both of those tools used for a lot less here on Buy & Sell.
Then for the rest, think about what would be handy:
- Set of combination wrenches
Screwdrivers
Pliers
Adjustable wrench
A 19mm lug wrench to get the wheels off
Tire plug kit
Spare fuses
Fan belt
Sockets/ratchets/extensions (including an Allen bit to fit the CV joints - I once had to reattach one by the side of the road)
Socket large enough for the fan nut (22mm or 24mm I think)
Scissor jack (You can use that on a less than flat surface, I think more useful and safer than the factory jack)
Jack pad for the receiver in the rocker (although a scissor jack can go under the suspension to change a flat)
You probably don't need all that around town, but I would want this stuff for a road trip.
Also, keep an eye on Buy & Sell. You should be able to find an original factory tool kit for $400-$600. Just be careful and patient. Many of them are offered as complete, but they are often missing tools. This is a complete Carrera kit. If you have a 1988-1989, there are some additional tools for the power seats:
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/1106159-1984-1987-tool-kit.html
Mark