'05 Hemi ?'s

I was planning on putting a cam in it and some type of header. Leaving the truck intake/efi, at least for now. I figure the engine will see probably 6500 and less rpms. The reason I say the 4spd/rpm thing is because of the possibility of missed shifts, staying the gear until the last once of power is gone and then shifting, etc.,

I've heard and read a little about changing heads (to eagle style). Do I have to change the accessories to match? I'm trying to do this on a budget. I want the car to be a driver ( LA to Phonenix, etc) I just don't want to blow it up by losing a valve when I could have prevented it. The engine has 42k on it. I heard it run before I bought it 7yrs ago. How do I check to see if it's been overheated?