96 Explorer- Steering Gear??

I have discovered that part of the steering system is leaking power steering fluid, quite a bit. I have to fill the power steering resivoir about every three days. The piece that is leaking is the cylinder that the power steering pump pushes the fluid into which then pushes out rods that turn the wheels. It appears that a seal may be failing and is leaking at all times, especially when the wheels are turned. My Haynes manual says that it is a steering gear and it looks pretty straightforward to replace. My question is: Does the stop-leak power steering additives work or do more harm than good; and should a replacement of the steering gear be done by a mechanic or could someone who is semi-mechanichally inclined with not all the specialty mechanics tools perform the repair. If I can do it any pointers. Any help would be greatly appreciated.

 

id suggest just replacing it as i dont believe their is a addittive that works well on a leak that bad.