Its a garage job. It will need vacuum pressure checked, dried and charged with the right mix of gas an oil if needed.
But if there is no gas in it, there is probably a leak...maybe a loose joint, maybe a dud compressor, maybe a rotten pipe, maybe lots of things. If the system has been empty for a while seals and o-rings might have dried out. Getting a/c thats been broken a long time working again is quite often a massively expensive job.