Seat removal/battery replacement-socket type required?
 

The bolt is 12 point. Does take a double hex or torx or ?? Thx

It takes what's called a triple square or XZN. They aren't always easy to find or cheap, but you will want to bite the bullet and buy at least a decent set if you own Porsches. I got a set of sockets from Sears for $30 last year. The brand was Capri Tools and they seem to be solid quality with a good fit in every fastener I have had a chance to use them on to date. The set I got has a few 3/8" drive sockets and a few 1/2" drive sockets for the larger sizes, if I remember right.

The change it itself is not hard, it took me about 45 minutes with the triple square socket. I adjusted my seat fully upright and rearward to allow me to tilt the seat once bolts were removed so I could remove the battery. To my surprise I had a lot of dropped money under my seat. Make to save your battery vent from the old battery and transfer it to your new battery.