If you post a schematic & parts list we can all help you troubleshoot in a more nearly logical manner.
Then the likelihood of changing out parts that are not causing the problem is greatly reduced.
Do you have a DVM?
Was it a 28 mV t'couple or a 750 mV t'pile or other? If it's 750 you possibly should see 3 ohms looking into the leads that feed the 'couple, with the couple disconnected. If it's zero or infinite the gas valve solenoid coil is bad. If it's 3 ohms and the pilot doesn't stay lit the valve could be bad for mechanical reasons.