I need help buying a Cummins.

I really like my 04 quad cab 2500. got it a year ago with 225k on it. I paid 12k for it. inside of bed is beat up but rest of truck is decent. 03-04 you can get the HO 305hp no emissions crap yet. Look for the obvious dents rust etc. engine wise unscrew the oil fill cap and just set it on the hole and with it running see if it tries to blow it off. you are looking for excess blowby. gives a easy assesment of engine condition. if automatic check the color and smell of the fluid should be bright deep red not brown. and just drive it and listen to it.