How long will it take once this dispute is resolved to show an affect on my credit score? And how much of an impact will it have?
I think the law is it HAS to be dropped after 7 years unless you dispute it and the company doesn't respond to the request, the bureaus will drop it.
Dispute it, and if they don't drop it, dispute it again until the don't reply and it's gone. You just have to choose a different reason for each dispute. But don't expect that to have a huge improvement on your FICO