I've had good luck in past dealings with UR, at least as a customer. I know where you are coming from though. You have a long employment life ahead of you and while you may really like your present job if there is no where to go then I would consider this move. BUT: How long will you be an "assistant" ? Pulling low boys is great when the weather is good and can get nasty when its not. Do you think you will move up soon? Is there high turnover at this location? Lots of questions! What are your benefits now and how does that compare with UR? At a young age with a wife and kids benefits almost outweigh higher pay. ( unless its a big jump ) I did this 9 years ago went from driving a service truck 50 K miles a year working on grain systems to a 50 mile 5 day a week commute as a electrical/mechanical tech, made slightly less at the time but benefits cost less and are really good. Does UR at least offer a "cost of living" ( bit of a joke) raise?
I'll add: I think you should go for it! You cant stay at a dead end.