"... when the wheel is turned at a sharp degree, it is not actually turning as far as it should..."

Don't exactly know what you mean by this. The steering system is designed so that if you lose power, it still will steer mechanically. I cannot imagine a situation where, when you turn the steering wheels, the front wheels do not also turn with it. Hard, maybe. Jerky, maybe. Clunky, maybe. Squeally, maybe. Noisy, maybe. But the front wheels will track with the steering wheel.

If you mean that when you attempt to turn the steering wheel, it resists you, then I would be suspicious of the PS pump, a loose belt, low fluid, a bad U-joint, or a bad rack.

"...was turning the other day...and the power steering squealed pretty loud..."

Probably a loose belt.

However, on a B230 engine, you might also have a failing front crankshaft pulley. The pulley is a two-piece item, much like a round "sandwich," with a rubber donut-like sleeve between the inner part (which sits on the crankshaft) and the outer part (which includes the pullies). When the rubber sleeve begins to separate from the inner or outer parts of the pulley, it can squeal and slip -- and if it slips it won't deliver power to the PS pump.

That means no or intermittent power steering.

"...when you replace the rack, you should replace the power steering as well..."

I assume you mean that you replace the pump as well.

Not necessary. Just flush out the old fluid and refill with new fluid.

"What do we look at regarding the rack..."

Leaks, torn boots (these can be replaced individually), and (radial) looseness.

"...tie rods..."

Looseness or (logitudinal) play of the inner and/or outer ends (ball joint like thingies). Outer tie rod end can be replaced individually.

"...ujoints..."

Typical failure is binding, so the steering becomes tight-loose-tight-loose as you turn the wheel through a full revolution. I had this so bad on one car that when the wheel was turned, it would stay turned and not return to straight by itself.

If you end up replacing parts that affect front end alignment (ball joints, tie rods, tie rod ends, etc.), plan for a front end alignment as the LAST step. (Don't want to pay for it more than once.)
--
Don Foster (near Cape Cod, MA)