Will it be hard to go through a divorce without a lawyer if a child iis involved but the couple agrees on everything?

No.  Usually, this is call a "Uncontested Divorce."  That means that both parties agree to all the terms and conditons of the divorce. And, both of you stipulate that the findings of fact and conclusions of law and order should be entered pursuant to your stipulation.

That said, because there is a child, you should consider hiring an attorney to ensure custody, child support, visitation, day-care and insurance are filled out correctly in the court documents.  Most attorneys will do a "Uncontested Divorce" for very little expense.  It may be worth it in the long run.

Hope this helps.