A lawyer doesn't "legitimize" documents, it is no more or less an NDA because a lawyer looked at it than if one had not. I have created and signed many NDA's that I did not have reviewed by legal counsel.
What a lawyer will do is to understand your situation, what you want to protect yourself against and review/modify the document to align the law and your intent.
So what you can do is to write down what you want to protect yourself against, who you are protecting yourself from, and then find an NDA that comes close to outlining what you want. You then take that document and intentions to a lawyer and ask them to review it.
As far as what to do if somebody breaks an NDA, that should be outlined in the NDA. If you have problems quantifying your loss or potential loss, then a court may find it difficult to award some amount in your favor. Part of your NDA may include the repercussions, the enforce-ability of which will depend on your jurisdiction.
If you suspect your NDA has been violated, take the NDA (signed) and the evidence to a lawyer, they will advise you of the next steps.