NDA Enforcement After scope creep with no amendment

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Illustrative scenario prepared by my practice.
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Hypothetical question

Has anyone dealt with something like this? I'm not sure what my options are.

scope creep with no amendment. I've been dealing with this for about 3 weeks now and the situation isn't improving.

The contract was signed 20 months ago. I have a copy of the original agreement. The total amount in dispute is approximately $42,000.

Should I hire a lawyer for this or try to handle it myself?