I feel when you bought your new machine the lady you got it from should have told you how long it would take for her to get to your machine.
She could have made an appointment with you to bring it in so that she could have her look it over. It shouldn't take her more then 5 min to know if the machine was running right .
if her service dept is that far behind then I would take her the new one back and pick up your Elna.
Find a store that has a better service record. The shop I have dealt with always had parts on hand and it was only a couple day for him to fix the machine. The age of the machine and the different thing you had going with it. She could have had an idea how much she would get for your Elna. If Im selling machine for my living I'm going to know the information I need to sell and resale machine its just like a car sales man