How far should I go with engine rebuild?
 

Hi, I need some advice. My 2010 550i with 138,000 miles on it is leaking oil, coolant and transmission fluid. In 2016 I have replaced the valley pipe and cover along with many gaskets, seals and o-rings. I did everything I could get to from top and bottom. Upper timing chain cover gaskets, valve cover gaskets, alternator bracket gasket and numerous others. All of the areas I addressed are still good and not leaking. But the car now leaks from areas that are not accessible without removing the engine and valve stem seals need to be replaced as well. Transmission leaks from the input shaft seals it needs to be removed as well. My plan is to take the engine and transmission out as one assembly. I will then disassemble them and replace all gaskets/seals and rebuild the transmission with new bushings, solenoids etc. my question is how far should I go with the engine? Does it make sense to replace piston rings and journal bearings? The car runs well, it just leaks every fluid possible.

If it were me, I'd just do those last few bits as well while I was in there. Parts are cheap, and you'll have a fully fresh engine to not worry about.