As for the R value, I’m not sure where to tell you to find that information. You might try a local lumber yard. They may have a chart with theR value of different thicknesses of wood. Putting in a window is not hard, but should be done to the window manufactures speciation. I would recommend that you contact a local contractor for this work. And finally, the log rotshould only be taken care of by a log replacement specialist. Call Ryan at 877-788-5647, he can help you with this project.