just had my tranny completely rebuilt...should I go easy on it for a while (3,000 miles) or what? Anything else I can do to ease the break-in process?

 

Who rebuilt it? Don't you think that would be where to ask. I don't know about rebuilt trannys specifically, but I know you should go easy on a new clutch for example. Give that new metal time to get used to heat and punishment. Same concept with brake rotors; you don't go out after you put them on, accelerate to 120 mph and then just put the brake pedal in the floor.