What do I need to know before changing a wheel?

Never been to a mechanic before but my car's right wheel got flat and I need to go to the shop to change it. Is there anything I should do or be aware of? I'm talking really stupid questions like - do I just drive in the area where they work on cars and park there or is there a line? How much should are typical payments and is overcharging common? I've never done this before and I have really bad driver's anxiety so any help would be appreciated thank you!