If you've found that you needed to replace the type but wanted to keep it's lay exactly the same there is no easy way to just select another type in it's place.
However after a bit of trial and error I found that with the gift of the offset tool it's very easy.
Use the select tool to highlight your entire "wrong" lay. Click the offset tool and set it's value in the bottom right box to 0.0000001 (if you set it to 0 oddly it default to about 0.1!). Lay your new objects by clicking it in the menu and then on the yellow boxes as you work along the route. You will have to reclick the item at each yellow box.
You will now have the exact same lay with both items. Then just select each part of the unwanted item and delete it, I found it easier here to select what I thought was the old item - they're in the same place so it's a bit of click and hope! - then use the blue up arrow to raise it to make sure it was the right (or wrong!) item. Then delete it. If it's actually the one you wanted to keep a quick ctrl-z will put it back and you can have another grab.
Hope this is useful, I was dreading having to relay something that had already taken me quite some time to get just as I wanted it
