I recently asked: How to identify cross-database queries in SQL Server
And the answer https://dba.stackexchange.com/a/176799/508, was extremely useful in helping me find a solution to the problem and I was intending on editing spaghettidba's answer to reflect what I found, to acknowledge the help. However my solution will require a nearly complete rewrite of the answer.
Should I edit the answer or add my own answer?
It sounds like you should add your own answer.
It would very rarely be the right thing to do to completely rewrite an existing (non-wiki) answer like that. Adding a self-answer to elaborate on the specific solution you applied to a more general answer supplied by someone else is not uncommon here.
You can also "acknowledge the help" with a brief remark and reference in your answer. You can also vote up the existing answer. You might also choose to accept that answer. It all rather depends on what you plan to write of course.
