I just visited Dell's Support page and got the following info, based on your Service Tag:
Original System ConfigurationThe processor is specified, but not the main board. So, you may need to contact Dell Support, or open the case to determine the manufacturer and model number of the main board.
Dias de verano is correct...these parts may be proprietary to the system and may cause conflicts, instability or failure. You may be better off using Dell parts only...but cost will be a big factor here.
What gets me is this comment you made:
I had a repair guy come today and he said it's either the Power Supply, Motherboard, or processor, which is what I thought it was and what people on here suggested. So, instead of paying 300 dollars to have them fix it I'm looking for some helping finding the replacement parts as cheap as possible, since I could install them myself.
I'm surprised the tech couldn't narrow it down...instead...you were given three possibilities. I hope you didn't pay this guy much...cause he didn't do his job.
The parts you are looking to replace should be bench tested...then you should go from there.
If it's not cost effective to take it to a repair technician for bench testing...I'd be looking into the possibility of maybe using the money you were going to spend for parts and labor on a new PC. It just seems like the most logical thing to do...if the processor, main board and power supply are all defective.