Question about tune up
 

How much does a 60k milage tune up cost on a mustang lx 1999. It has 70k miles on it now, will I still be able to drive another 1-2months before I get the tune up?

tune ups are recommended not mandatory your car will not stop working if you don`t do it at the specified time. the only real important thing is the engine oil and tranny fluid if it`s a auto and the air filter

When should I change the timing belt?

never i have never seen or heard of a need to change the factory chains change the tesioner though yes but hardly ever is this needed to be done

I would take the time to look at your plugs and see how they're doing...

It will also give you a general signal on how well your car is running...

I changed my timing chain for the first time at 140000 miles. May I waited too long maybe not.

At 60,000 miles you'll want to get a new air filter (if it's dirty), a new fuel filter, fuel injection service (cleans deposits from injectors...gas quality is pretty bad right now so it's fairly important), automatic transmission service (recommended every 30,000 miles...make sure to ask for a new transmission filter some places use a machine without changing the filter). Also it's not a bad idea to get a coolant flush since aluminum head engines are sensative to electrolysis - turns coolant acidic.
It won't hurt any to wait a couple of months to get it done.