It would be great if you could just file a dispute and forget about it, but you may have to follow up. Especially if an item is very old, the creditor in question may have been bought, merged or gone out of business entirely, which makes documenting everything important.
Keep notes of the people you speak with at the bureau or lender, when you contacted them and the date by which any corrective action will be taken. Check your credit report again after that date to make sure they followed through. The three credit bureaus "talk" to each other electronically, so a correction made on one report should be reflected on the other versions, too.