1990 Lexus ES 250

This car is used mainly by my 2 sons, who are both in college. The power steering was leaking and the car began to make a loud noise. I took it to a mechanic and was given an estimate of $1100. I have two questions. The first, is this a reasonable estimate? Secondly, would it be wise to spend this amount of money on a car this old? So far we have replaced the alternator and had some minor electrical work done.