Where to start?  There are 2 series Aurora, the first 95 to 99 are all near
identical. to the 95. Only one available engine and I think actually only 3
available options, sunroof, chromed alum wheels and an Autobahn gear ratio
package.  Lots of standard features, heated power seats both sides with
lumbar controls, leather.  All are powered by the 4.0 version of the
cadillac Northstar engine.
The second series is 01 to 04  (there was no 2000 Aurora) is a complete
redesign, smaller body and far less distinctive. Hard to tell it from a
Maxima or Altima, or even a late model Taurus. Yech.   In this series there
were fewer standard features, more options.  Heated seats no longer
standard, power on pass side an option etc.  Now came standard with a 3.5
v-6 "Shortstar", a Northstar with 2 cyl. lopped off. 4.0 now an option.
   I have a 96 and tho I love the drive and looks it's been the biggest
piece of sh.t I've ever owned and I've owned a lot of cars.  The Northstar
is a very sophisticated engine and superior design, uses a split crankcase
with the crankshaft mounted between the crankcase halves for a vastly
superior lower end, something cadillac had lacked for the previous 12 years.
Unfortunately 95-96 Northstars were prone to an oil leak between the case
halves, corrected in later models.  About a $6 dollar gasket and almost
$2000 in labor.  I've had numerous electrical faults, the oil level
indicater has never functioned properly.  Intermittant high idle that's been
impossible to diagnose.  Premature rusting below the gas door due to a
leaking body assembly gasket (requires long drawn out explanatin),  problems
with AC, seat controls, window controls, trans overhauled at less than
80,000 km., (50,000mi), lifters failed in the front head only, and a host of
other problems.

But, as I said earlier, a hoot to drive once you figure out how.  It's real
old fashioned performance, poor low rpm power because of the camshaft design
but really comes on over 3500 rpm.  Will walk a stock 5.0 mustang from a
light but has to catch him after the first few feet.  By learning to drive
it I meant you have to drive it like you're mad at it.  There's a button on
the shifter labeled norm and power.  My is set to power all the time.  What
that does is put the trans shifts a little higher up, into the power band.
You have to keep the rpm up to have available power at your toe.  If you
stand on the pedal from a dead stop it will move away from the stop okay,
but as the tach hits about 3500 - 4000 it will really start to pull and the
tires will start to squeel, a long time after you've left the light.  The
redline is 6300 I think and it feels comfortable when it gets there.  Not
hanging up and freewheeling with no power when it shifts.  Wide open
throttle and exhaust sound like high performance cars of yore, but with all
of the comforts of a luxury car.
Hope all of this helps.
Steve G.