You should have made an appointment back in September, or earlier. Most places will be booked solid this time of year. If you didn't, go to Vermont Tire and Service. They don't do appointments, and operate on a first come, first serve basis. Show up at 5:30 am (they open at 7:30), dress warm, bring a chair/book, and get in line ahead of the crowd. You'll have it done right away if you hang out, or done that day if you take their complimentary shuttle. Their shuttle will take you anywhere in the Burlington area and will pick you up later at your given time and place. I've used it to get to and from work before.

Try and get an appointment somewhere, but if you can't, this is a surefire way to get it done ASAP, it just takes a little more effort.