I think there is a middle ground here. I would go in, explain nicely my issue. As I read this the issue is - my machine has been here since __date__ for what started out to be a simple repair. I've been very patient, but I bought this machine so I can use it. I understand you are only here 1 day a week and that perhaps this has turned into more than you feel comfortable tackling. __the other shop__ will take it if you feel you are in over your head on this one, if not, can you do it now and I'll come back in an hour to pick it up.
that's my thoughts - you would still be kind, not angry, offering a option, setting a deadline. Your project deserves to be pushed to the head of the list. A now statement is fair and reasonable.
I think sending your husband would be a mistake since this is also a quilt shop you apparently like. If he gets angry and causes a stink, you might hate showing your face there again. Also the fact that you can stand up for yourself in a calm and reasonable way will show them that you deserve and expect to get what is fair and you will not be walked on so don't think you will turn me into a doormat on other things as well. This event will set the tone for future transactions such as defective fabrics etc.