Got a chance to buy a 97' 2500, Auto, 4x4. The truck has 220k on it, had the auto trans rebuilt about 2k ago. The owner says he was pulling a trailer and the water pump went out and engine locked up on him. So whats an engine running and whats involved with changing it out {unbolt & disconnect the old one and put the new one in} or do I have to worry about ecm/pcm's etc. ? Any help and advice would be appreciated, thanks!