Again not a step by step guide but just what is possible.
The Casio MD-703 Shrouded Diver. This watch is from the late 80s... Dead, requiring battery change.
Time to get out the tools. Since this has a screw down case back....
The case back...
The removed case back.
What you see when you remove the case back. The module half covered by a spacer cum battery holder.
The spacer cum battery holder.
Another view.
Old battery.
Battery removed, ready for new battery.
The new battery.
New battery in. Remember not to use metal tweezers to insert the battery.
Battery in, gasket lubricated, spacer in. Ready for the case back. Check for any debris or dust.
Case back closed. Do check the watch is working before closing the case back.
Don't forget to lubricate the gasket.
All done and in full working condition.