Before you pick it up MAKE SURE EVERYTHING WORKS CORRECTLY. Do not accept/pay for unit until you see everything work. SOme places count on your eagerness to take possesion to not do a thorough job of fixing all the problems before selling the unit to you. YOU WILL NEVER be in a better bargaining position as you are now. THey want your money make them earn it. Otherwise you may find yourself waiting weeks and weeks to get a problem fixed. This forum abounds with horror stories about poor after the sale service.
The place you bought the unit is not your friend. They want as much money with as little effort as possible.
INSIST on a complete walk through with the fridge on and hot water heater working, hooked up to water supply or water tank filled. Check AC, Furnace etc do not pay until satisfied