Changing the gearbox oil asap will prolong and extend the life of the Rover Midland gearbox fitted to early MINI's, ignore BMW's 'filled for life' policy because they won't pay for a new gearbox out of warranty.
Instructions are on here if you search....you need 2 litres of MTF94.
Make sure the BC1 (Body Control module) in the drivers footwell has the later black plastic water shield fitted to avoid future electrical glitches due to damp.
If the power steering cuts-out or does any unusual things like running when engine is switched off, be prepared to replace the pump......not a big job if you can do some diy mechanics.
Above all enjoy driving what is a great car to own and fun to drive!