Actually its not in the transmission unfortunately you cannot see the transmission by pulling the sump pan only when you split the motor. Now the front bearing of the output drive does get fed by the same oil as one of the transmission bearings. they are both sealed on one side only and get oil from a passageway in the engine block the rear output bearing original design gets oil by good will!!! What oil runs out the steel seal on the front bearing migrates back to the rear which is not the best way. On the updated transmissions the rear bearing is a sealed grease packed unit and the front bearing is still sealed but with a nylon type seal which keeps the oil more contained to the two bearings in the block. A much better design IMO. since yours took so long to fail I suspect it was not in backwards like some were (including mine) which failed real quick. this was because the assembly bloke drain warm ale for lunch instead of a proper chilled beverage like us in the USA
I doubt you will be able to tell on yours unless the seal is still in tact enough to see where it was located. If it was in backwards then your lucky it lasted as long as it did. This means one of two things 1.) God likes you 2.) you should buy a lottery ticket as you are one lucky SOB
depending on whether you have some mechanical aptitude and can read the manual you can do this work including the internal update on the transmission. It might take you longer then 16 hours but what the heck count it as taking your time to do this right. You can also update the transmission and output drive without loosing timing between the cams and the crank. There is a different style of cam chain guide that comes with the update kit but even though yours does not have the same type it will function for the life of the chain. This is my opinion as I have collected all the different types of guides Triumph has used to figure out what the engineers were doing plus figure out the best set up for when one uses real stiff valve springs like the type used in the Carpenter kit. Call it reverse engineering the engineers thought patterns. Of course if you want to change it out with the kit this can be done at any time whether the engine is in the bike or not. Perhaps some spunkier cams also. It can also be done at a later date while the engine is in the bike although it is easier to do it while its opened up. It really depends on whether you want to change the clutch cover gasket twice and remove the electronics on top of the engine twice.
Anyway I rambled on enough already.
Carry On
