When I replace the images in the dll file does it need to be 256x256? that was not made clear in the tutorial.. So I am wondering what size I need.
Take the icon I placed in the above example .... here is the snip from IcoFX with that icon opened .... tell me , what should I say about the size ? It contains, as apparently visible, 256x256, 128x128, 48x48, 32x32, 24x24, 16x16 .... almost all the possible sizes that are required in various places throughout the system.
An icon, if properly made, is of this very characteristics. Almost all the icons you may download are of this type. Unfortunately, if you use a flat (single layered) icon, it should be as large as possible. But, there is a little problem. take the example of a HDD icon. It is shown in the explorer window, as well as in the navigation pane. A single icon ... when in explorer window, it should be 256x256; and at the same time, when in navigation pane, it should be 16x16.
So, an icon usually means a normal icon as I described . I cannot recommend you to use a flat icon, due to the reason I have described above. I hope , the particular icon you are trying with is of a normal icon as I described. If not, you are to use the best available size, no doubt.
If it is still not clear, let me know :)