i'm going to try to help you out here. shouldn't be that big of a deal. on the underside of the p/b lever.....there is a copper colored rod in the handle it's self. thats what activates the locking mechinism. the spring just slides right in from where it fell out....if you notice on the end of that little knob there is a hole.....thats where the copper colored rod inserts........long story short...all you really have to do is slide the spring back in....followed by the little plastic knob...make sure that little rod lines up with the knob...or it won't stay together.
oh...if that little knob is broke....find a junked stang....pull it right off......it is on there pretty good too! hope this helps man.