Agree with counsel. I would add that if the modification request represents a significant increase/decrease over time (simply project the claimed decrease, or increase as the case may be, out over the period of time until the children reach majority -- basic formula subject to change, but at least it gives you an idea of where it could go), then it is ften cost-effective to get a local lawyer involved.
The lawyer can actually be a cost-effective safeguard.
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