Lots of great comments here, but I especially agree with jvr826's about the oil analysis. They are very cheap, and will give you a wealth of information as to whether the engine has suffered major damage. You should definitely tell them in the "comments" section of the submission form about the overheating episode, so they can pay special attention to the aspects of the analysis that might pertain to to the impact on the oil of overheating.
But to get the maximum bang for your troubleshooting buck, I would do the following:
1) Warm up the engine
2) Do a compression test. If this shows an obvious problem like, well, low compression in one or more cylinders, stop, and start searching for a replacement engine
3) If the compression looks OK (not sure what the spec is, but the readings should all be within about 5% of each other across all the cylinders), drain the oil, and fill the oil sample vessel after letting it drain for a few seconds, like jvr says (the idea is to take the sample about midway through the drain), send the sample out for analysis, and pray.
Edit: I just reread the OP's post. 10+ miles driving with the engine overheated?! Your brother needs a serious talking-to. When my daughter first got behind the wheel of a car, one of the very first things I told her was, "See this gauge? If the needle EVER gets close to the red line, immediately pull over and turn off the engine."
Last edited by Variocam; 11-24-2011 at 08:11 PM.