lightened flywheel would be quote good on your car elfman would make it pick up much quicker and as it has plenty of torque there shouldn't be too much of a trade-off when pulling away or climbing hills on the cooper s it's a bit more involved than a cooper or one but the general parts removed are the same... loads tis... whats your chassis number and i'll get the particulars for you
disconnect battery
remove intake filter housing
drain gear oil
remove front left wheel arch trim
remove bothe driven shafts with steering stub carriers
remove trottle assembly
remove suction pressure sensor
remove impact tubes
remove front subframe
secure engine in installation position using special tool
remove top engine support bracket
remove bottem engine support bracket
remove manifold heatshield
remove shift cables
remove clutch slave cylinder
remove supercharger inlet pipe
remove starter motor
release trans. mount (upper right hand engine mount)
lower engine zapprox 135mm release trans bolts and remove trans.
then it's just case of removing the clutch (if your repalcing the fywheel it's probs a good idea to change the clutch too then lock up the crank and unbolt the flywheel (it'll be loctited on and i'm pretty sure we replace the flywheel bolts as a matter of course..
then rebuild in reverse order and refill with gear oil
quite a big job but imo i think it'd be worth it