My mom's 528xi has an N52 engine. Be aware that the block is a magnesium alloy which means you have to replace a lot of the bolts whenever you take them out (i.e. if you replace a belt pulley, you need to install a new bolt with it.) There is also a
well documented issue with lifter noise. BMW released a revised head on all new engines after 11/08. Other than that, the engine is bulletproof. Typical issues are small things like oil leaks from the oil filter housing, valve cover, and eccentric shaft.