how much is involved in changing my wheel bearings.. is it just 3 bolts after the caliper and rotor are off, or does it need to be pressed in/out of the knuckle?

No need to press it out or off but there is more to it than just 3 bolts.
jack up car, use jack stands, remove tire
you will need a 34mm or 36mm deep impact socket to remove the wheel hub nut in the center.
Remove the caliper and pads, then the brake rotor.

Now you can remove the 3 bolts for the bearing assembly, the top center is tough to get at, you will need to loosen it off half way then rap the center shaft back for better access to remove the bolt (you will see once your head is in there).

Install in the reverse order, put a little dab of grease on the end of the half shaft splines before inserting into the bearing.

I just replaced mine this weekend. Not a bad job. I needed front rotors and pads while I was in there, so I killed two birds with one stone.
Not a bad job, but allow some time.
Ben

Same thing applies to your Aurora Oats, I had to change my hub and it was a total PITA, the wheel speed sensor ring was stuck inside the spindle, making it a nearly impossible DYI job. I hope for your sake everything goes ok.

G-body cars are notorious for bad wheel hub. Everyone I know that has a 2000-20004 Bonneville, Classic Aurora or Seville has had an issue with a hub just short of 100K miles. :?

I just replaced my right front hub assembly last week with only 65000 miles on the car.

ive got 84000, i noticed play when i put the tires on at 70k.. its not making noise but it has some play in it that will fail state inspection

Well at 137k miles the drivers front wheel bearing just started making noise on the SSEi, so I'll be replacing it very shortly, but definately no problems before then.

Shawn