1999 Buick Park Avenue Nose cone replace only or replace wi

The nose cone on this vehicle was replaced @ 33,000miles. It is now @ 66k and the nose cone started leaking oil out of the pulley shaft seal after an 800mile trip. A rebuilt nose cone goes for around $300 and the nose cone and blower assembly is about $450. Both have a 3yr warranty. Does the blower wear out after X# of miles? Would it be more economical to replace both now or just the nose cone and wait for another 30,000miles and then do both? I just found out that the auto manufacturer oil level spec. for the nose cone is too high. I was told that this is what may have caused the seal to fail, no place for the expanding oil to go. Is this correct information? Does the oil need changing sooner than recommended in the manual? if so how often?
I would appreciate your advice in this matter. Thank you.