Lightning is terribly distructive when it comes down the phone line. The modem can be destroyed by very small amounts of lightning voltage. But if everthing else works, I would assume the new modem is just improperly installed and he needs somebody locally who knows how to do it.
Modems can be very difficult to install, because of the way the drivers are put back into use, and the methods for testing the replaced modem. If he got a different modem, he will need different drivers, and each brand and model of modem can have different ways of installing these drivers.
A good tech or knowledgable friend should be able to fix it in 10 or 15 minutes.