When we service a machine and it doesn't work when the customer takes it home, we want to sit down with the customer and see if we missed something. Or, if it's user error. I'll bet your sewing machine tech would be glad to sit down with you and figure out what the problem is, without charging you anything.
When you say the "feed dogs froze," do you mean that they won't pull the fabric through? It could be that the presser foot tension dial got bumped? It's on the top, left side of your machine. Set it to the highest number and see if that helps. I can't tell from pictures online, but it probably has a feed dog drop switch on the back of the machine. Make sure that's in the correct position, so the feed dogs are up. Set the stitch length knob to its highest number, then turn it down to the length you want.
I hope you're able to get your machine sewing again.