To access the pulleys for servicing:
1. Remove fan clutch
and set it inside the fan shroud.
2. No need to remove Fan Shroud.
3. Apply force Clockwise on the "lower" Pulley (aka Tensioner Pulley) to release tension on the drive belt and slip the belt off.
4. Now you see the "Idler pulley", check to be sure you have Torx or Allen screw and remove it. Straightforward:
If you are strapped for cash. Info on re-packing the pulleys is here:
http://www.bimmerboard.com/forums/posts/2001611. Note how the pulley is assembled, including washer orientation for re-installation.
2. Use a picking tool and gently remove the seal and you will see the bearing. There are a total of three (3) bearings: 2 on the tensioners and on deflector (or idle pulley), while there, you may as well grease all three of them:
PS: You can dip the bearing in a small container containing gasoline to rinse of old grease. Then pack new grease in and re-install the seals.