Dishwashers are standard and holes SHOULD be standard if nobody raised the floor or lowered the counter (or the cabinetry and current DW are old and off).

Should be an easy DIY job. Should be! :)

Technically all DW's fit in a 24" space. Practically, there are other issues beyond just the basic will it fit in a 24" opening. Are your cabinets inset, full overlay, or partial overlay? That will affect how well the panel looks with them. Inset panels tends to stick out beyond the face frame, and not look quite right. It really has to be planned for from the beginning for deeper cabinets if it is to line up. Full overlay is fine. Partial overlay can be too, if the cabinet maker knows what he's doing. Are your cabinets relatively newly installed? Wood changes color as it ages, and some paints do too. If the cabinets have been there a while, the panel that you get from the cabinet company or cabinet maker may not exactly match your current cabinets. It may catch up in time, like cherry darkening, or it may not, like some paint fading.

We were a month or so away from starting our remodel when our old dishwasher broke, so we bought the new one we were planning to put in the remodel - the stainless one. I used it for 2 months, and discovered that I don't like stainless. I had time to change my ice maker order to a panel ready, but I figured I'd just keep the stainless dishwasher. But now I think I'd like to just change it to the panel ready. The cabinet maker already made the place for the dishwasher. I didn't want to change if it was going to be a problem.

So nothing has been painted yet