If done at a pro shop they will want to do a compressor, Filter/dryer, orifice tube/expansion valve as well as a complete refrigerant fill. Some back yard mechanics will not do all the above and still be able to do an adequate job. Speak with other mechanics in your area and get some more quotes as $1000 seems a little high. I usually do them for around 300 to 500 bucks (depending on the cost of compressor and filter/dryer)