1994 BMW 318I 124K miles failed smog and may need timing belt replaced? Any cost estimate, ball park figure?

Car was shipped from MA to CA. Trying to figure out how much money to spend before it is not cost-effective. It is otherwise well maintained and done 30K, 45K, 60K, and 90K miles recommended maintenance according to the owner's manual, etc., at a BMW independent shop. New to CA; need to find a trustworthy BMW independent shop!