It is a pretty involved affair. But in general you should...
a) disconnect negative battery terminal
b) remove upper engine covers
c) detach jump-start terminal and tranny dipstick (do not pull out dipstick housing for oil will spill)
d) remove airduct (to and from microfilter to bulkhead) if needed
e) detach intake manifold and cover alternator with protective material
to prevent oil or fuel from falling inside it
f) detach pressure pipes at injector but loosen only at fuel rail (caution fuel is under pressure), then remove injectors
g) injector may be stuck and require a special puller
h) sealing rings between injector(s) and cylinder head should be replaced
i) re-install removed components with proper torque settings
g) if more than 2 injectors are replaced, injector map adjustment should be done with a BMW GT1 diagnostic machine.
h) roadtest and recheck for leaks
Please note that this is only a general description, requires special tools as needed, adherence to torque settings, etc. plus a healthy dose of common sense.
Do not proceed with these repair steps if you are not experienced with engine repairs.
