Toyota Repair: Alternator?, toyota 4runner, tow truck driver

Question
We have a 1990 Toyota 4Runner 6cyl SR5 automatic transmission, 4dr with 174,000 miles (with a factory installed security system). Head gaskets were replaced about 2 years ago along with a new water pump, timing belt, and battery. (The starter was replaced before the major engine work was done.) About a week ago we got into the vehicle and drove it 20 miles. When we tried to start it to return home, it would not start.  All lights across the dash came on and the radio would not work.  We jump started the car and tried to drive it home but after about 15 miles it slowly lost power and died on the freeway. We then had it towed home. The battery charge gauge indicates the battery is charging when being jump started, but when the cables are disconnected, the gauge slowly starts falling below the halfway mark.  We took it to an auto repair shop and had the alternator replaced yesterday at the suggestion of the tow truck driver.  We had told the auto repair shop that "we thought it was the alternator but we were not sure." We drove it home, turned it off and about 20 minutes later got back into the vehicle to go to the store and the car would not start.  We spent $343 for the alternator replacement and we're very frustrated at spending that kind of money only to find it not starting.  Any ideas on what might be causing this vehicle to not start?  The auto shop had the vehicle all day 8:00am - 4:00pm and when we went to pick it up we got the feeling they did not know what was wrong with it even after replacing the alternator because of the way they acted when we asked if it was "fixed."   We have only driven the car about 14,000 miles since the major engine work (head gasket, water pump, timing belt, and battery replacement). Thank you for any assistance you can give.

Answer
The last time it did not start were you able to jump start it? It still sounds like the alternator is not charging, especially if all the warning lights on the dash come on when the engine is running, I'm not exactly sure what is going on here but that's what it looks like to me.
I would take it to another shop or the toyota dealer and have the charging system tested, I think you will find the problem there. Or you can go back to the shop that replaced the alternator, they should have tested the system after they installed the alternator to make sure that the problem was taken care of.