The DD-258 is simply a discharge certificate. The benefits that come from service are dependent on the charachterization of service. So, for example, if you received an OTH discharge, you would not be eligible for benefits.
As for changing the records? I think you have an uphill battle.
Hi, My name is Philip. I am an attorney with over 16 years experience. Hopefully I can help you with your legal question.
Is it possible to modify a discharge (to "upgrade" it from "oth" to "honorable")? Certainly. That is possible.
The Board of Corrections for Military Records can do this.
However, it is by no means automatic...
In order to grant an "upgrade" the board of corrections will require the applicant provide evidence of "error or injustice". Only when provided with compelling evidence of error or injustice will the board of corrections make a change to a military record. The board of corrections grants the military with a "presumption of regularity"...basically they presume the record is correct. The burden to rebut that presumption is on the applicant.
So...if you want to change your record? You have to prove there is an error in the record. For example, if they discharged you improperly AND you can prove it? That would be a basis for upgrade.
But unless you have such evidence, the board is not going to make any changes to your record.
I am very sorry to have to bear bad news.
Please let me know if you have more questions. I am happy to help if I can. Otherwise, please rate the answer so I may get credit for my work.