well I learned this the hard way, but when I had my timing belt and waterpump replaced at a shop something really bad happened. After they put the timing belt and finished the rest of the job< I drove it back to school. On my way back, the waterpump broke into 2 pieces which caused the fan to drop and almost destroyed my radiator. The shop took it back and showed us the "aftermarket" waterpump which was in 2 pieces. When they redid the timing belt they put a genuine Infiniti waterpump and fixed the radiator free of charge. So just a warning that the aftermarket waterpump might break. The aftermarket one they showed me was alot thinner metal than the Infiniti waterpump, so if you want to save trouble and time go with an Infiniti waterpump. As for the belt, you could probably use an aftermarket. Something on this caliber shouldnt matter.
-Josh Sharpe