[Steve Tinker]

fivepointnine - you are falling into the trap most people do when estimating a job.
You start the clock when:
Someone gives you the keys, you then have to move the seat(s) & raise the roof into the service position.
Remove the rear parcel shelf and carpeting.
Remove the access port (10 bolts I think).
Only then can you get to the 24mm tensioner bolt to remove the belt.
Go to the stores / receiving to get the new belt and install.
Run the engine to check rotating OK.
You then have to reinstall all the above & do the paperwork - I would say 40-45 minutes would be a fair estimate.
Of course, if you smoke, have diarrhoea and have a talkative girlfriend, that gets added onto your account too...... But don't worry, you own a Porsche so you must have plenty of money !!