98 dodge avenger es 6 cyl., won't start at times, wierd?

replaced serpetine belt, air conditioner belt since then car won't start sometimes. engine size is 2.5, was told for the alternator that the whole motor needs to be lifted out and intake manifold needs to be taken apart just to get to the alternator, crazy! when the car won't start the radio and lights still work! we jumped it the first time and nothing, had to take the connectors off and clean them then jumped and started, ran for an hour shut it off and dead! replaced the battery ran good for a day, next morning dead again! Brought it in was told alternator is bad, brought somewhere else to have it installed and was told its fine, never replaced that. i have to have my battery charger with at all times cuz you never know if the car will start once its turned off. Any ideas?