Affirmative. The 09 CRF450R onwards (that run the 48mm KYBs - not the showas) will fit the Sachs perfectly. All the seals and bushings will cross over. Back when I last ordered I found the whole kit for $50. Prices have gone up since the Tsnami but if you shop around you might find a bargain.
As for air gap (springs out, fork collapsed) I think specs are between 90-135mm. If you're happy with it as it is now I'd suggest measuring before you drain them out and you'll have a setting to get you back in the ballpark.