97 Taurus Wagon - Ball Joint Replacement

Just had my brake rotors replaced for warpage for the fourth time as the car passed 100K. My mechanic told me that the driver's side front suspension
ball joint was badly worn and should be replaced ASAP. Unfortunately, he told me, on the 97 Taurus, this requires replacing the entire steering knuckle assembly, as the ball joint and stud is an integral part of it, and cannot be replaced separately.
Questions:
Urgency of repair - he said the ball joint it was pretty loose, but car handles fine and has had no unusual tire wear patterns. I do intend to follow his advice and repair ASAP, but is the car OK to drive in the meanwhile?
Does anyone make a repair kit so only the ball joint has to be replaced on the knuckle?
Should the lower control arm also be replaced? I would think not, unless the tapered hole to receive the ball joint stud was excessively worn.
Typical parts cost and availability for the knuckle? - mechanic said it was a dealer only item and in the several hundred buck range. I have a World Parts Locator Super Search out on it - that service has saved me a lot in knowing what I can get "dealer only" parts for - I have used the quotes to leverage my local dealer to sell at best price.
Typical labor hours for the repair?
Why the heck would Ford make a commonly replaced relatively inexpensive part, expected to wear out at some point, an integral part of an expensive component that would likely NEVER wear out? (I think I just figured that out, but it has nothing to do with engineering!)
Thanks in advance,
Chris Bowne Stonington, CT
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This is turning into a preplexing one.....NAPA and Autozone both show avaialbility of relatively inexpensive replacement ball joints for the 97 Taurus. They appear to be designed to be a press fit into the steering knuckle, which apparently is how the orignal Ford components are assembled by thier supplier. However, the Ford dealer's part list indicates that the ball joint assembly in the steering knuckle is not replaceable. My mechanic say that he advises against a press fit replacement, that he tried several times and had poor results with the new joints fitting in properly, and in one case it actually seperated. I guess considering the consequences, I will bite the bullet and fork out the bucks for a new knuckle assembly with integral ball joint, but I still think its a lousy way to design a component known to wear within a normal car lifetime.
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The ball joint is pressed into the knuckle, and is removable. It is pressed in and a large snap ring is installed. If the incorrect tools are used to press out or in the ball joint, yes poor results will happen as with the replacement of any part.

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