I had this problem with my 1998 Sable... Cleaned the door latch mechanism with something like brake cleaner and then followed up with liberal amounts of spray lubricants. Actually had to oil the drivers door a couple of times over the first few months. Been good ever since (4 years).
Work the oil into the latch my opening/closing it a few dozen times. Neighbors might think you're a little weird, but mine didn't blink an eye...
My 1998 does that to me - I keep a can of spray lubricant like wd-40 handy. A good drenching, slam the door a dozen or 2 times and it'll behave for another 8 months.
Could be sucking air into intake.
Lack of or absence of maintenance such as oil changes and fluid levels.
I have the same problem on my 95 Sable LTS
There is a redesigned transmission vent that should fix this problem.
the air conditioner and heater are two separate things.(not connected) ;) it may have a fuse. or the it could just be bad.
The heater core could be clogged up.
Try Autozone.com - they have a comprehensive on-line repair guide for the 1996-1999 Taurus/Sable.
Could be a bad inertia switch.
I don't think are multiple types of catalytic converters.What might be different could be where it's located - dependent on if your car has single exhaust pipe versus dual exhaust pipe system.
20 to 40 minutes depending how quick the mechanic is.And for the backyard mechanic or novice just getting started with doing their own repairs, this one could take 30 minutes to an hour or so.See "Related Questions" below for more about Taurus/Sable thermostats and other such stuff.
the engine
Depending on which engine you have, an alternator could range from $140-195 (USD) at Autozone.com.