I presume you have the name and address of the other driver. Take your car to two reputable car repair places ( I like ASE members, as they have a certification you can point to) and see if they will give you a written estimate of the damage. You can use that in a small claims court action.
You can dispute the debt with them and ask for validation under the FDCPA. But generally, they only have to give you what their clients gave them, so hey might not have any more info than the number. Send them a letter by certifid mail or priority mail asking for validation in terms of when teh debt was incurred, when the date of last acitvity was, and if they can tell you what is principla and what is interest. You might find this account is tiem-barred.
2 issues. If the salesman came to teh house an dyour dad signed at home, there is a 3 day cooling off period. It's NYS' " Door-to-Door" law. Secondly, there are enhanced penalties under GBL 349, but you would have to show deception. Do you have the facts?
Unless you expect to need credit from now til then, I wouldn't bother. Let it roll off naturally. Sometimes, as you fear, you can cause yourself more grief. The squeaky wheel gets grease: sometimes it gets trashed.
The man was concerned enough about his fence and your practice of piling your snow on it to put a sign. If there is damage to the fence that he can prove, you may well be liable. Also, if he put the sign there because this ( snow and fence bending) happened before, he will be convincing in a small claims court circumstance, in my opinion. Be careful.
Generally, you want to keep your utilization at @20%. Obviously, a good paying history will help your score, but you may need more than one card or credit to give you the boost you want. Consider a car loan. Or another card, say, a store card, that you use once every other month but generally keep i n your sock drawer. That will help