Adjustments to the tension rod are usually limited to "fine tuning." If there is a serious warp, I believe that most repair shops would apply heat and tension to "undo" the warp.

While the process is not particularly complicated, it is best done with proper tooling, and benefits from an "experienced hand." Depending on the amount of correction needed, removal of the neck and fingerboard might be needed to prevent damage elsewhere. The necessity for disassemb depends partly on how bad the warp is and partly on what kind of tooling is available to the person doing the repair.

I'm relying mostly on what's in a couple of "how-to" books, supplemented by very minimal experience. If possible, it would be best to get someone with some experience to take a look at it, if possible, to get advice on how serious it is.

John