Q: Is a consultant must for implementing ISO systems.

Probably you could buy a copy of the ISO 9000 standards and attempt to do it yourself, but this will probably lead to higher cost and more time to achieve certification since you will also have to employ specialised people for the job who may become workless after certification is achieved. Such people being employees may not enjoy the degree of freedom which a consultant would enjoy. You may achieve certification eventually, but your quality system will probably not be effective and efficient. You must find a good consultant who not only has a track record of helping clients achieve ISO 9000 certification, but also has the ability to improve the way you operate