Of course if you are going after the vanos seals, replace the valve cover gasket & spark plug seals. The valve cover gasket may be plasticized and welded to the top of the cylinder head, necessitating slow, careful prying and separation with appropriate tools (putty knife etc); flex the plastic cover too much and it may crack.
Be sure to have a small torque wrench that's designed for very light torque specs and that's accurate in either direction.... The vanos piston bolts are reverse-threaded (turn CW to loosen) and will take only 6-7 ft.lb of torque.
edjack mentioned replacing the vanos solenoid O-rings. That's a job you can always do separately at a later date if they give you problems, but it should be much easier to remove the solenoids when the vanos unit is off the car.
This is also the perfect time to refresh the entire cooling system with new parts because you have to remove the fan shroud and expansion tank to have good access to the vanos unit.
Oh yeah .... about your alternator. It's possible to replace the regulator unit without removing the alt from the car. If the bearings in the alt are not shot, the fault is almost certainly the regulator. Of course, it never hurts to have a spare alt on the shelf, so don't throw the broken alt away. Someday you may want to try and refurbish it.