My '91 Honda Civic DX slipped the timing belt. Of course, it won't start. Mechanic says it will cost around $375 to fix, and , I may have bent the valves which will cost WAY more than that. My question is, (1) Is $375 a reasonable price for replacing a timing belt? And, (2) If I didn't hear any clanking or banging when the engine lost power and died, you think my valves ore O.K.

First- welcome to the Wonderful World of Automobile Neglect! You are not alone, junkyards are full of late-model once nice vehicles who's owners saved a lot of money by never doing any maintenance until the vehicle failed to move under it's own power.

Second- You are either misunderstanding or misquoting your mechanic. $375 is a reasonable price to replace a timing belt BUT once it has slipped he is not replacing it as much as he is investigating how much damage is present. A reasonable fee for investigating the damage is 1 hour shop labor time, usually about $70. Any competent mechanic will be able to discover the damage and create an estimate for repair in 1 hour.

Also- Your valves are bent. If your cylinder head is salvageable it will need to be rebuilt and if you are exceedingly lucky all of your pistons are still in one piece and not shattered aluminum slag in the bottom of your oil pan. Just because you do not hear sounds like pots and pans banging together in a dishwasher your engine is still mortally wounded. Manufacturers recommend timing belt replacement at 60K-80K miles not as a way to force you to pay the dealership but because they have very smart people who have determined that your engine's timing belt will not last much longer than that and failure to change it will have dire consequences. Honda's are infamous for this. So are Mitsubishi's, Toyota's, Nissan's, in fact every single car with a flexible poly timing belt will need to have it replaced at regular intervals. Take heed- $375 every 60K miles is a lot less than Ferrari owners have to pay every 15K miles ($4500), in fact it is even less than rebuilding your engine every 80K miles ($2700) because the timing belt slipped and destroyed the engine.

Hope that helps, and please continue to deeply distrust your mechanic and refuse to do even basic maintenance because as you are discovering you are vastly more qualified to determine the maintenance requirements of your automobile than the manufacturer, the engineers who built it, and even the people who make their living ensuring your car starts every single time you turn the key.

First of all, the maintenance on the car was not my responsibility.(I had bought it only a month ago, and when the belt slipped, it was the first time I had driven it since I test drove it.)
Second, I paid the mechanic the $375 for replacing the timing belt. He started it up and it ran just fine.(He said I was lucky though)
But thanks for your enlightening and informative (albiet sarcastic and self-rightious) answer.