a guy told me that i can make my 350 run better at higher rpms by changing the wates in my distrbuter. is it true and will it make me lose power at the low end? or shorten the life of my distrbuter?

Maybe make an improvement, maybe not, depends on what you're starting with, engine and vehicle.

Won't hurt the distributor but can hurt the engine if too much advance is put in too soon the engine will ping which depending on how hard and hot varies from an annoyance to holes in expensive parts.

Bogie