You need to run from that repair shop fast! Any repairman that tells you a threader has anything to do with the head has no business touching a machine. I would get a estimate in writing from them, describing the problem, and solution with part numbers and prices..(tell them it's for your husband )then I would email that directly to Viking main office.You can get a new threader here...less than 50 dollars retail, and install it yourself
https://www.sewingpartsonline.com/ne...129420-01.aspx