Volvo Repair: Time to fix/replace all valves or buy new car, volvo 960, independent shop

Question
We have a 95 Volvo 960 with about 195,000 miles (mostly freeway commute miles)

One part of the timing belt system literally broke
off (plastic part).  The mechanic initially thought
it would be a $300 range job to replace parts of the timing belt system.

After working on it, they now suggest we need to
replace ALL valves in the car.  It's a $5k job!
Is it worth it to fix it?  The car is 11 yrs old.
All maintenance is done by an independent shop
specialized in Volvos.  Will other parts start
"wearing out" besides the valves?  How much longer
will the engine last?  Any ideas/advice is appreciated!  

Answer
Ella, thats what happens when you dont change the timing belt at 70 thousand miles, the belt breaks and it bends all the valves.  He is a little high on price, but it is around the 4k range to properly fix it.  What broke?  Its up to you if the car is in nice shape, etc.  They are nice cars.  The valves dont wear out but like I said, they bend if the belt breaks.  The engine will last Many more miles if you keep with the services and the belt changes.  I have seen those motors with over 500,000 miles on them.  Roger