I understand that it sits in the end of the alternator, but can you replace it without taking the alternator out of the car?
Yes, you can change the regulator with the alternator still on the engine in the car, but you must know what you are doing and you work from underneath.
Someone also mentioned that even adjusting the belt is difficult, but that depends. First remove the adjusting nut, washer, bolt and square spacer. The square is such that it cannot turn within the bracket as it's sides contain it. So you weld the bolt to the square and now you can slacken or tighten the nut with just one hand and spanner. Easy!!
Roy