Helpful Hints for changing the oil...

Frequently, the cannister cover will be very difficult to break free.  Use a breaker bar with CAUTION!  You may need a 'low profile' socket due to the limited space available.

If you loosen the filter cannister cover enough to break the seal, it will help drain the oil from the filter as you drain the oil pan.  Less mess later!

When replacing the O-ring, save the old one just in case (will explain later).

When replacing the O-ring on the cannister cover, make sure you lubricate the O-ring with PLENTY of fresh oil before you install it, and lubricate again after it is in place.  If you fail to do this, the O-ring will bunch up and cause a leak!

The new oil filter should be 'pre-seated' into the base and cover before installation.  Take the filter (plastic side down) and press firmly into the base until it is fully seated.  Remove and do the same into the cannister cover.  This reduces the resistance from initial seating.  You can leave the filter seated into the cover and screw the cover back onto the base, or you can leave the filter in the base fully seated and screw the cover back onto the base.

Getting the Cannister Cover started into the base is a little tricky - having the O-ring well lubricated will make it a little easier.  Start the cover onto the base carefully, confirming the cover is 'square' with the base to prevent cross-threading.  Once you have it started, you will still have resistance from the new O-ring, but you should be able to get the cover well onto the base by hand.

Torque the cannister cover to 18 lb-ft. 

The factory Drain Plug gasket is a plastic gasket that is molded into the Drain Plug.  Best to replace the drain plug at every oil change.  The cost is minimal compared to headaches from a leaky plug!  (The linked filter part numbers above includes a new drain plug.) 

Torque the Drain Plug to 18 lb-ft as well.

You can also use a magnetic drain plug that will help trap microscopic metal debris and can be re-used.

Fill with a name brand FULL SYNTHETIC motor oil.  It should take close to 4 quarts.  MINI recommends oils in SAE classes 5W-40 and 5W-30.  MINI likes Castrol Synthetic, many MINI owners use Mobile 1 Synthetic.

After you confirm everything is buttoned up, and you have fresh oil in the engine, start the engine.  The red Engine Oil Pressure warning light should go off in a couple seconds.  After a running the engine for 30 seconds or so, shut off the engine and let sit for a few minutes.  Check for leaks, and re-check the oil level. If everything is dry and the dip stock shows 'full' - go for a drive!

If you run the car and find a puddle of oil under the engine, there is a good chance the O-ring was damaged when you installed the cannister cover.  Take the old O-ring that you saved, and re-install - with care!

To reset the oil service reminder, see this article .