89 lesabre

89 Le Sabre 3.8 v6 Could someone please help me out? My moms lesabre just all of a sudden started acting up. Sometimes it runs great and sometimes it doesnt run at all. Here is what happens, the car will run fine, but if you shut it off, most of the time when u go to start it again it turns over and trys to start but just spits & sputters for a second then it just cranks and cranks. Its almost like its not getting any gas. Sometimes when you push the accelerator the engine just goes silent like its not running but as soon as you let off the gas it returns to an almost perfect idle!! But what i dont get is why it only does this sometimes. I just put new plugs in it hoping that would help, but no luck. I've been told it could be the coil pack, fuel filter, fuel pump, injectors, etc. etc.... Is there any way to check these withought being charged an arm and a leg by a mechanic??? Any help is greatly appreciated, my mom really needs her car back!