The CRA is responsible for monitoring the reported DOFD on the OC account, and excluding the charge-off from your credit report no later than 7 years plus 180 days from the reported DOFD.  You need nothing except monitor your report to ensure it happens.  A dispute would not be appropriate, as the issue is not one of inaccuracy of reported information. To attempt earlier exclusion, you can try sending the OC a GW request. 

If the charge-off remains in your CR after its required exclusion date, send a complaint to the CRA for their violation of FCRA 605(a)(4).

How much score increase you are likely to see depends upon whether you have any other remaining major derogs.