Timing chains typically should not need to be replaced for the life of the engine.
Timing belts are another story - there is a manufacturer's spec regarding mileage, typically between 60,000 and 100,000 miles. This is an important maintenance item - should the belt fail, you will be dead-in-the-water. Additionally, with some engines there is catastrophic valve damage as the timing is lost and the valves crash into the pistons. Not a big problem with American cars, but rice-burners are notorious for this type of damage.
Need to know what engine you have to determine whether it has a belt or a chain. Being a Firebird, I would suspect a chain.
The brake pads themselves are about $15-$30 per axle. However, if a shop does the work - look to pay quite a bit more due to labor and markup, particularly if they recommend turning the rotors - probably on the order of $80-$150 per axle, depending on the scope of work.
Water pumps generally don't get replaced until they show signs of failure, which is typically a leak. The coolant quality is important, in that the anti-freeze also serves the purpose of keeping the seal lubed.