Interesting that it is countersunk on one side of the flange but not the other. Some spokes have the J-bend fully used and some without it being used all that much. But with the heavy duty spokes, I would not worry too much about that.
If your new rim is the same effective rim diameter as the old, it should be fairly straightforward re-lace. If the new rim is different, it might still be OK to re-use the spokes if it's within a mm or two of the old rim. You'll need new spokes if the two rims differ much more.
Before taking the wheel apart, verify the number of spokes and the cross pattern used. Measure a couple of the spokes once it's apart and write down the number of spokes, cross pattern, and spoke lengths (some wheels require this due to cross patterns and hub flange sizes). Also write down the model hub being used and the rim type. That way if you ever have to replace parts, or re-lace again, you'll know what materials are in that wheel and what you need to repair it.