String Trimmers

Have a 128CD String Trimmer which has a broken throttle trigger. Since replacement part looked different than installed part I called Husqvarna to get installation instructions. Was told new part did not have spring so was a different install, but no installation instructions were available. Have always gotten support for my 2246 lawn tractor and my Rancher chain saw. Why do the line trimmers not have the same level of support? Right now I am looking to buy a new trimmer unless someone can help with this repair...and it won't be a Husqvarna.