Zane, if you need to update a lot of assets, Mass change as per Leslie's advise is the way to go.
but since it is just one asset, you can just change it and save the asset in the Asset General window.
it should prompt you to do a reset or recalculate...
to be safe, i recommend restore a current backup of your live data to your test company and then do the change there first. the change on the asset general window may trigger some entries in the FA financial detail.. depending on what you select....