For starters, if something is not addressed in your agreement, then she's not violating your rights. Unless it's in the agreement, it doesn't exist. You most certainly can't even consider a contempt filing over something that's not in the agreement.
Also, you can't complain to the court about a 'prospective' change in circumstances. They're only concerned with what has happened, not what might happen. And I don't see any court in the world which would object to her remarrying (some would object to her living with the person before marrying them, but depending on how long, that might not even be an issue).
I would suggest that you use very neutral wording and prepare the modifications you'd like to see. Then get someone else to look at them to make sure that they're fair. For example, it's common to say that someone can not have overnight guests (other than family members) when the child is in the house. It is NOT reasonable to say that someone can't have overnight guests at all.
Do NOT retype the existing agreement. This only leads to confusion. Rather, write the proposal as changes to the existing agreement. For example, "the words 'xxxxxx' to be inserted after the phrase 'yyyyyy' in section 13.b of the agreement. Or ' Section 14 to be added, reading "zzzzzz".
Then, after you've prepared this, you have two choices. You can submit it to the court saying that it has become clear that certain important issues were not addressed and ask the court to allow the modification. Or you can submit it to her attorney and request that you agree on the terms and submit them to the court for final approval. (I guess you could also ask her to go to mediation to work out the changes).
The 'right' answer will depend on the circumstances and your particular judge. If you go to the judge and they're not amenable to changes, they could slam the door on you right away - and then you can't raise it again. Therefore, without any other information, I'd be inclined to offer the changes to your ex and state that you're willing to discuss the specific wording, particularly with a mediator.
In the end, the agreement is only going to work as well as the two of you are able to work together. Even if you get 100% of what you want at this point, if you completely destroy any ability that the two of you have to work together, then you've lost in the end. So be careful about collateral damage.