You can look up timing belt replacement in RepairPal's estimator to get an idea of the cost for that service. The problem with a broken timing belt is that there is a good chance of the broken belt having caused additional engine damage. The technician won't know until he's in there.
The workshop manual states the engine must not be rotated during timing belt replacement or damage may occur to the valves and or pistons. This engine is listed as an interference fit engine, indicating components will collide if the timing belt breaks.