S52s are fantastic motors! Engine rebuilds? The only time I can think of that is with moneyshifting or FI. I've never really seen a NA S52 in dire need of a rebuild nor a catastrophic failure.
My old E36 M3 took a beating and never left me stranded. I'm talking drive down to Deal's Gap 5 hours away, drive all day, drive home, and do it again next week.
If you have any specific questions let me know, but it sounds like you already know what's going on with the car.