The valve cover gaskets have a tendency to leak oil, especially the one near the firewall.
2004 Toyota Camry Problem Reports
RepairPal Verified 2004 Toyota Camry Problem Reports
The Check Engine Light may illuminate because a component of the oxygen sensor stops working. As a result the engine computer is unable to determine the proper ratio of air to fuel for the engine. Replacing the failed oxygen sensor should correct this concern.
One or more motor mounts may wear out on cars with high mileage. This will put extra stress on the other mounts, and the faulty mount(s) should be replaced.