1997 Dodge Neon Loss Coolant while driving

Urgent expert opinion needed. Car in repair shop. Loss power and stopped while driving in highway. Noticed loss of coolant in reservoir. Had I towed to nearest town repair. Mechanic said they will change the timing belt and water pump but no guarantees it is the only problem. Mechanic says I might have overheated causing vent valves at which more $$ repair costs. It is an old car, more sentimental value than practical reasons for keeping it (passing on to son for his first car in HS). Is the mechanic right that there could be cascqading problems developed from loss of coolant and failure of the water pump? In your expert opinion, is it beyond economical repair? Thank you very much for your advice. Sincerely.