To be absolutely sure, Yes, you have!
It is not neccecearely due to the CPU, but you are intended to exchange the mainboard as well.
As you mentioned, the chipset is different.
You can also try it another way first beceause if it works, it is a lot quicker!
If there is a safe mode like in Win98, start in it, and delete ALL the hardware info.
(In Win98 to be found in Control panel, System, Devices)
Then shut down and rebuilt the computer. (DO NOT let him detect hardware right now!)
If anything is working with the new mainboard and CPU, start your OS and let it sort itself and the new hardware out.
If this works, you do not have to reinstall the OS and all the apps.
You can reinstall the OS and the apps if this will NOT work.