My brother is looking at a 2001 250 with 155k miles. It has a TS 6pos with custom tunes by advanced diesel? I haven't heard of them. The only downside is... The auto tranny is about to go out. The guy with the truck says he has a warranty on it as the tranny was rebuilt not too long ago. He lives in Cheyenne & had it rebuilt in Denver(where I live). Is this a good idea?