The OE heater is very difficult to locate. Assuming he has the 1.8L L4, he can order
Zerostart part # 3100129 from Amazon. It is a cartridge style heater. There is a machined port on the right rear of the engine block that it inserts in. It requires removing the air filter housing to gain access. There is no need to drain any coolant. It is a little more difficult with a manual trans because the clutch piping bracket needs to be unbolted and lightly tweaked for clearance. Someone with limited mechanical ability should be able to install it. If the dealer won't install it, find a local independent shop who isn't afraid of earning some money.