Oky Doky.. heres the low down.

Im getting a 1994 Giant road/race bike to add to the stable for my backup commuter.
Am building a set of wheels from a sora rear/ultegra front hubs to slap on her. The rest of the bike has all the org componets...so the question is should I upgrade or leave it as is?
Only problem with org stuff is left side down tube shifter.. the little plastic pice that looks like a washer around the screw that holds it on??Is broken.. it still works fine ..but i know its broke and it bothers me...I like to have my stuff 100% and cant find a replacement part for the shifter..so should I upgrade or keep looking??

Advice.. suggestions?? What would you do?