The reason the dealer is quoting you a high price is because installing Air Conditioning to a car that doesn't have it is not like just buying an air-con unti and bolting it on.
An air conditioning unit has a pump inside which is usually driven by the cambelt - this means changing the cambelt and installing a new pulley or two. Other modifications have to be made as well to the car's air ducting and air intakes.
If you look at how much work has to be done, and how many things have to be changed - you'll understand why it costs so much.
If you still really wan to give it a go yourself you may be able to find out what parts you need from your local Hyundai dealer / garage - this would be your cheapest alternative.