You are looking at an initial filing fee of just less than $300. The process can be quite simple if you agree on everything (although I would recommend that you get it put into a legal document by an attorney for your child's sake). Since you have a child, you are also looking at some more fees for a class on parenting. Divorces are not cheap, unless you can agree on all of the details, and even then, you are looking at several hundred dollars between the two of you - only in filing fees.
If you do not want an attorney, then you can get a good start with access to the right forms at http://www.courts.state.co.us/Forms/Forms_List.cfm/Form_Type_ID/108