hi,
the 328i engine is more or less bullet proof in my opinion. for me there are some minor leaks around the valve cover and also the oil pan. both which can be easily changed. just need to make sure that the cooling system is in good condition, ie: radiator, expansion tanks, hoses, water pump, thermostat. other than that the engine not giving me prob. my prob is the gearbox, which i now converted to manual.
hope my 2 cents helps.