Can I just get a whole new door from a junk yard and it be ok?

You do not state the make and model, but in principle Yes you can get a serviceable door from the same car at a scrap yard and apart from changing the locks over it should fit without problems.

This has certainly been the case in the past, however modern cars may have a lot of electronics attached to the doors, and changes to these modules may not be apparent, so to be on the safe side you would have to find a car that is identical to yours to ensure compatibility.

If your local dealer is friendly you could ask them for advice as they would know all the variations and changes made to that model over the years. You will have to provide them with the serial numbers of both cars of course so that they can check their records.

If you are lucky you might even get a door in the same color ( might be a shade lighter/darker differant batches of paint) if you do it might just be a case of getting it home taking the panel off and changing the door lock which is easy enough you might need to swap the panel anyway.

Give it a go easy enough to do.