You can replace Nords, High Elves, or Wood Elves with the green folk. Khajiit and Argonian don't work, as their armor is different to acommodate their tails. I decided that the Bretons, Redguards, and Dark Elves weren't appropriate to replace, as they are the primary races for Daggerfall, Sentinel and Wayrest respectively.
The mod doesn't attempt to replace the verbage of the character creation, or change the map, so you'll still create your character as one of the replaced race, but you'll see a choice of Orc faces, and the character's race will be correctly reflected in the in-game dialogs.
I found two different sizes of FALL.EXE depending on what patches etc. I had installed, so the install scripts will work with either of those. If there are other versions of it, the install should fail safely without affecting the game.
If you try it out, please report back here, so everyone else knows of any problems you hit.
Get it http://ghastley.org/daggerfall/docs/orcs.html - link is at the bottom of the page.