Hi, The affected part of the board is the DRAM power supply. To replace them you need to remove them with heatgun or soldering iron. Then resolder the new ones with soldering iron. I recommend a youtuber called Louis Rossmann. On this link you have the schamatic and board view.
Sounds like a disk... But it could also be the fan. If you hear the hard drive this is wrong model. I don´t think the hard drive had problems. If it would be a hard drive issue it will boot up to a blinking folder with question mark. Try reseting the PRAM or the SMC.
The problem could be a logic board. But I think it is the MacSafe Dc in board. First check so all the plugs are plugged in. If all plugs are in I think its the AC in board. You can also ask your friend if you can test he/she charged battery in your mac. If that do so your mac start it is the AC in board. Sorry for my english.
Try to boot from the installation DVD or make a Bootable USB and see if the disk appear in Disk utility. If it´s appear you can verfy the disk. You can also boot from linux and see if detecting it. If not I think it´s dead.