Before sweating details, get the correct axle to crown measurement.

Measure the fork yourself with the bike leaning on the wall.

Next account for sag by wrapping a pipe cleaner, cable tie, or similar around the stanchion, then sitting on the bike. Sag will push the wrap up and it will stay there. Get off, measure how far it moved, and subtract that from the unloaded length to get the sagged length.

Once you know the sagged length, you can make smart decisions regarding the replacement. IMO dropping an inch or less probably won't cause issues, especially if the rake is increased. However, combining drop with reduced rake may cause some handling issues. On the bright side, gravel riding is less sensitive to steering issues than on the road.