Changing common elements to limited common elements.

Our homeoweners would like to purchase some of the property behind there homes that is currently listed as a common element on our plat.By purchasing this property it would change into a limited common element.What would we need to do and what steps would we need to take in order to do this.We are in colorado and I already am aware it would require them to purchase the property also to change our governing document and the plat.If any has done this this year and knows about what it might cost that would also be helpful.
Thanks