I use Redline 20/50 in all my car's never had a single oil related problem. Don't forget the mini transmission and engine share the same oil! always better to change more frequently. I change oil every 3,000 miles on mini's if used. Every 6 month's if not used frequently. It's cheap insurance really.

Annealing is the correct word.  It re-softens the metal so it doesn't become brittle and crack, so that makes some sense that you could do that to reuse the copper washer...since it would hypothetically just squash flatter rather than cracking under pressure.

I'm in the Valvoline VR-1 20-50 club, for the added zinc. And changing every 2500 miles or so is a good idea no matter what oil. And I have a long 15/16 wrench to loosen the drain plug, but a shorty 15/16 to keep from over-tightening. Lesson learned the hard way. Oil filters vary in quality. I have settled on NAPA Gold 1374, which may well be for the aforementioned Dodge Neon, but just ask for the number. I actually use a new or renewed copper washer each time. You can anneal them by torching them red-hot then plunging in water. I have not tried simply re-using one without annealing, but they're dirt cheap to buy, and even cheaper to anneal. (Anneal may not be the right word, experts...)

The point of all this input is regular oil changes prolong your engine life no matter what oil you use. Filter is important though.

I have used and re-used the same copper drainplug gasket/ring X 12 yrs. No leaks

If you have the magnet tip drain plug, and the oil has not been changed much, you will see some swarf from the gearbox.

Expected. Just wipe it off.

Most folks use 20w-50.
Brands for that and the filter will almost always bring out a heated conversation. [rolleyes]
Be very careful not to over-tighten the drain plug. I've had really good luck using a rubber/metal gasket. (washer) You can almost just finger-tight the drain plug. I think the size is 14mm.
//www.cgenterprises.com/gaskets_rubber_metal.htm

Edited to add: Since the car is new to you, check the torque on the wheel nuts. (40-43 ft/lb) One of the most common screw ups on these cars is to "go gorrilla" on the poor little things.... They're only a 3/8" thread.
If they've been over-torqued, you might as well figure on replacing the studs. Better for you to chose the time than the stud making the choice.

Welcome to the mini world! 

Big Long debate always goes far here regarding oils - This that this that ....

New oil is better than old burned up oil. 

Fact - 20 W 50 is the weight to use. and it takes 5 solid quarts (slightly more if oil cooler (but you dont drain the cooleer) so 5 quarts.

Most tend to stay away from Full  Synthetic oil.  Although there are changes in new oils of today vs old oils - and protective chemical additives  - called ZDDP -  Its a lubricant ( good for our old motors) not found in new oils of today.

Personally i use Castrol GTX - 20w50 - 14K miles last year no issues.

Have used Brad Penn - 20W50 - Its oil - Has ZDDP additive- Worked Fine. 

Others have used mobil 1 - etc. others- Valvoline Racing 20w50 (has zddp) etc

Pro tip -  The spin on filter is the same as on a 1997  Dodge Neon== Simply go to the parts store and get that filter for your car, and 5 quarts of oil you choose. 

Have fun...

1982 998cc, 27,000km on the clock (reality is, probably more).

what type, weight, brand, etc should I use? 

Any other her tips? 

thanks.