Did you already pay for work done?
If you did, then I'd simply ask for my gun and money back. If it's not already finished, check to see if you can just get your gun back and go with someone else to install/repair it.
This time of year is very busy for people. Christmas shopping, christmas planning, final exams for those who are in university.
When someone asked me how long it would take to get their camera fixed, I'd just give them a rough quote, that's the best we could do, however when someone comes back a week or three later yelling at us telling us that it's been too long, well sorry, but there are other things happening in the world that are not directly connected to your life.
Give it time, or ask for your gun back and fix it yourself I figure.