Here's why:
* Pressing/Removing the bearings: This is the biggest challenge. You'll likely need a bearing press or puller to get the old bearing out and the new one in without damaging the hub or bearing. Improperly pressing the bearing can ruin it.
* Hub Nut Removal: Removing the hub nut often requires significant torque and a strong impact wrench or an air wrench. A breaker bar may also be necessary.
* Access: Access to the bearings can be somewhat tight, requiring careful maneuvering of tools.
* Potential for Damage: If you're not careful, you can easily damage the ABS sensor, brake components, or the spindle itself.
* Alignment: After replacing the bearings, it's highly recommended to have a wheel alignment performed to ensure proper handling and tire wear.
In short: While doable by a reasonably competent DIYer, it's a job best undertaken with experience and the right tools. If you're unsure, taking it to a mechanic is the safer and potentially cheaper option in the long run, especially if you damage something in the process. A YouTube video demonstrating the procedure on a similar year Camry is a helpful resource *before* you start.