I advise that you just take it in.
I do my own tires frequently, but it does require some equipment, and it's strenuous.
First, you need a bead breaker. You cannot get the bead off without a tool that's designed for the purpose, and if you try something else you can damage the sidewall. In a pinch, you might be able to place the wheel under a vehicle, and use a jack to pop the bead, but it would be trickly.
Once the bead is broken, you need two good tire irons and a small hand sledge.
Lay the wheel flat, kneel on the tire so that the bead is pushed into the drop center of the wheel at one side, and then start prying it up and off 180 degrees from where you have pressed it down. After the first foot or so of bead is off, it's easy.
Now, stand the wheel up, take a tire iron, and using it as a lever, start, at the top, prying the other tire bead off the same rim edge you pried the first bead off of. Put the lever in and push it as far over the top of the tire as you can. The tire will be distorted, and there will be a little of the bead off the rim. Now you can remove the rest of the bead with the hammer.
Voila, the tire drops to the ground undamaged. The mechanic drops to the ground nearby.
Do not attempt if you have a bad back.