How to update a map myself?

[Growltiger]

I have a map in Oruxmaps format, with files OruxMapsImages.db and mapname.otrk2.xml
It is a simple single level raster map.
There is an area of the map I want to update, and I have a digital file of the updated area.
I want to get the tiles, edit the ones that have changed, and then put all the files back together again, replacing the files I have now.

So is there a way to export into all the component files and then combine them all again?
(I can edit the tiles using Photoshop, if I could only get to them.)

Thanks.

[Growltiger]

Never mind, I eventually figured it out.