[ppbon]

... and I wouldn't want yellowboxter01 (or anyone else for that matter) to replace some expensive parts only to find out that those weren't the ones.

When is an appropriate time to change the fuel pump? Once in the cars lifetime, well past the 75,000 mileage mark.
The appropriate time is when it fails. Why would you want to replace something that might never fail? The pump is not a replaceable item like the fuel filter (on older 986s)

there is a buzzing noise for about 5 seconds and then it quits.
Thats normal, Its your Vacuum pump running to aid in heating up the O2 sensors, it does it everytime you start in the am and sometimes on short breaks between driving. The ECU decides.
It's not the Vacuum Pump it's the Secondary Air Injection Pump. And yes, it is normal, especially when the temps gets colder.

When should I change the struts, certain number of miles or what? old struts are ready to replace by about 75,000 miles.
Again, why make a blanket statement like that? If a strut isn't bent or hasn't leaked, it's still good. Mine are the OEM M030s and they've only seen 191,000 miles to date.

Also, the ignition switch used to make a solid clicking noise when I pull the key out, I've noticed within the past week that it doesn't do this anymore. Is this a tell tale sign that it's on its way out and I should replace it?
Its the Ignition lock mechanizim, not the Ignition switch. Probably gummed up and not dropping the steering lock pin into the steering column.
With 99% certainty it IS the Electrical Portion of the Ignition Switch, and NOT the Lock Mechanism. It sounds counter-intuitive, but that's the way it is. The plastic parts in the electric portion tend to crack, which then don't allow the lock mechanism to work properly. It should be replaced, once it starts acting up.

Happy Boxstering,
Pedro