i am supprised you even managed to get the part on its own? - i have done a few of these on other cars - you need to take the regulator out drill out the old rivet from the arm making sure the drill bit is slightly smaller than the hole, fit the new one and using a centre punch and a big hammer "tap" around the centre of the rivet so it expands (and is realy tight) - make sure the other end of the rivet is square and the metal end is contacting a flat hard surface (vice etc...)while doing this.
Clean and regrease the runners then refit and realign and all shoud be ok!
ian loud
May 2010