where is the starter on the STS and how do i change it?

What year?

If you have a northstar, it is probably (I say probably because I don't know all about all years of N*, still learning about my '99) under the intake pipes. Take the plastic cover (DO NOT START ENGINE WITH THE COVER OFF) off - 4 acorn nuts, then lift gently to take a peek - it's on the driver's side between the cylinder heads. To some, it is easier to replace it there than the standard beside the oilpan locations

I understand you have to remove some intake plumbing, but it's not like, say the SB chevy and ford intake removal/replacement...

Let us know how it goes.