I've been in the field for over 6 years (working for a big company) oversee thousands of machines. I've replaced a cpu maybe five times. Usually when the heat sink got stuck and bent pins.
Other technicians I work with don't really troubleshoot very well. They replace main board and cpu together. I'm against this. Cpus rarely will ever fail. So, to serve a purpose. If you immediately think it's the cpu your wrong. Troubleshoot elsewhere.
I usually remove a stick of memory to verify memory. Then swap memory i took out with the one thats left. Then I pull cmos battery turn on, turn off, then put battery back in. Next I check mainboard.... It got off topic but this is a searchable item.