Hey paul.
If your crankshaft bearings is ok and you find the right oil mix about 3-4% i think and the speed kit is brand new or 100% ok there should be absolutely no truoble. If you by a brand new kit you will have to drive slowly and nice the first 350 km, because if you dont kiss you speed kit goodbye.
But remember this thing if anyoine teels you to do something drastic get a second opinnion