Plugs come pre-gapped from the factory. As long as you buy all NGK or all Bosch from BMW you should be fine. As for the 325i, the plugs and coils have the same part number (I think) and the blocks are identical. This DIY should work with any N52. You can probably use it with an N54. It will be slightly different but an engine's and engine. My friend's 540i has a similar process except he as 8 plugs obviously.
If you see oil in the hole where the coil goes, your valve cover gasket is leaking. Not a huge deal but if you see oil in there you should think about replacing it.
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here!
| Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors