So you own a 8IGHT RTR and don't know which bearing is which.......very sad. Try taking the clutch bell off and learing a thing or two about your ride.
As for the whole bearing thing, pro-tek sell 10 packs for both sizes. Clutch bearings take a severe pounding and don't last too long so don't think they will be there for a long time. If you try and use them when they are bad they can stall your motor and you will wonder what is going.
I get one race day from my clutch bearings, which adds up to about maybe an hours use if I take it easy and try and be really smooth on the throttle.
The best aluminum options would definately be the shock towers, shock caps (top and bottom), rear bearing inserts, centre bearing adapter, alum. servo horn and maybe the servo saver top but I haven't even put one on mine yet.
The stock plastic parts are fine, I wouldn't worry about getting the aluminum ones but if you like all that stuff then go nuts.
I haven't brocken any plastic parts yet after 14 months of racing and general use. The CVD condoms are a great idea and have them on both of mine.
I haven't tried carbon disks mainly because I still have good brakes with the stock ones.