Is there a tire center here ?

Yes

Yes. Drive around the left side of the building. You'll see parking and an entrance there.

Yes, back left side

Yes, drive around the left side towards the back corner. Unless you're already inside, then you can just walk over to that side. You can even order tires online that they don't currently have in stock. Thats what I did, ordered some cheaper tires.

Yes they're one.