I managed to change my alternator recently and have to say that the feeling of accomplishment achieved was priceless....with the help of the 101 projects and a little common sense these cars as high profile as they are, are remarkably easy to work on... plus the good folks on here help too :)

One item to add...if you have the time.

Once you have your alternator out, go have it tested. In many cases, the failing piece is the voltage regulator, which bolts to the back of the alternator. An auto parts store test will tell you if you have a bad diode (internal to the regulator) or a problem with the alternator itself.

If you have a bad VR, its easy to replace with a ~$50 Bosch unit.

I went this route almost three years and 20K miles ago. So far, so good.

Does anybody know the torque values for the two 15mm bolts holding the alternator in place?

32 or 33 ft lbs. Can't remember.

Just did this project last weekend. My bushing wouldn't budge with a heavy small sledge. Instead I used my air chisel. Worked great. Took seconds. Had the alt out and the new one in in under 10 mins.

36 ft-lb for the bolts holding the alternator in, per Porsche manual (for the Cayman 2006).

Also, in bold letters, the manual say you must install the drive belt in the same direction it was spinning before removal - don't flip it around.

WHILE YOU ARE IN THERE:
1. Check and if necessary R&R the brittle ,leaking Oil Filler Tube. It will eventually cause bewildering vacuum leak issues and CEL's. Access is awful but a little easier with the alternator out.Pelican has a diy.
2. This is a rare opportunity to get to the Knock Sensor on that side.
3. Replace the Serp belt
4. Check all the pulley bearings
5. Particularly check for wobble on the w/p and P/s pump
Others should add more to this little list?
6. When you reconnect the battery - there is a correct sequence that involves 2 short waiting periods while you pray to the DME & Immobilizer gods - check the owner's manual or Search Initialization.
Be prepared for a struggle with the concealed 15mm bolt head behind the Tensioner pulley .See Search if it is a problem.
7.Consider testing/replacing the SAI system components that are concealed behind the alternator.

Two more steps
 

Two more steps for mptoledo's 10.5 step list:

.3: Open top halfway to service position.

.4: slide both seats as far forward as possible.

.5: THEN you disconnect the battery. And limber up so you don't pull a muscle contorting yourself to do the work.

Just take the passenger seat out. 4 bolts and less than 5 minutes. It makes things much easier.

NOW ya tell me. Thought about, didn't do it, then regretted not doing it, then considered re-connecting the battery/wondered if it would be worth the extra trouble. In the end, I got the alternator/belt back in without too much trouble, but I DID almost pull a muscle. For reconnecting the plastic clip connection at the back of the alternator, I found it easier to do it by reaching around left-handed from behind the driver's seat.

Seat out, top in service position. ;)