Weed Eater One

I bought the Weedeater 1 from Sears about a year ago and the first day I got it, it wouldn't start. I spoke to Sears and they took 3 weeks to come look at it and the tech sprayed starting fluid and got it to start. We used it that day and picked it up for the winter. The next summer, we had the same problem and called Sears again. This time they had to replace the carb. on it. It took them 2 months to get out to check it, 2 weeks to get the part in and 2 months to come put it on. We used it twice after that and started hearing a clicking noise coming from under the mower. Called Sears again and 2 weeks later they sent a tech out again and this time, the tech didn't even look at the mower. He said that problem has occured on that mower for a long time and the part is impossible to get. He told me the part if they could get it would be $300-$400. I only had the mower about a year now and was only able to use it 3 times with a lot of problems. I pulled the cover plates off today to see what exactly was the problem and it isn't that hard to change. is there anyway I could get the part through warranity sent to me and I just change the part myself? The part I need is the transaxle kit part #532436144. From what I have read, this is a manuf. defect that the old part (original) has been changed. Please advise. I can do the work myself so you won't have to pay labor warranity.