I have been looking at buying a 2001 f350 4x4 crew cab long box. The truck has 150,000 miles on it. It had a new 7.3l installed about 12,000 miles ago. What can I expect for things like fuel economy, maintenance issues or any other surprises? I have heard they have transmission problems. Is this something that will need to repair every X amount of miles, or is it a one time fix? Any help or advice would be appreciated.