1) The Revised 3rd Edition books will not impact T20. It will add some material to the SRD, but I haven't heard that any of it's going to be radical changes, simply some new feats and class changes, none of which will impact T20.
2) Treat Darrians like normal humans. The big difference is in background and skill selections for classes, and those can be modified by the Referee to fit the milieu.
Hope this helps,
Flynn